P. 153 of Theorem List - Intuitionistic Logic Explorer

Theorem List for Intuitionistic Logic Explorer - 15201-15300   *Has distinct variable group(s)

Type	Label	Description
Statement
Syntax	ccxp 15201	Extend class notation with the complex power function.
class ^c
Definition	df-relog 15202	Define the natural logarithm function. Defining the logarithm on complex numbers is similar to square root - there are ways to define it but they tend to make use of excluded middle. Therefore, we merely define logarithms on positive reals. See http://en.wikipedia.org/wiki/Natural_logarithm and https://en.wikipedia.org/wiki/Complex_logarithm. (Contributed by Jim Kingdon, 14-May-2024.)
|- log = `' ( exp |` RR )
Definition	df-rpcxp 15203*	Define the power function on complex numbers. Because df-relog 15202 is only defined on positive reals, this definition only allows for a base which is a positive real. (Contributed by Jim Kingdon, 12-Jun-2024.)
|- ^c = ( x e. RR+ , y e. CC |-> ( exp ` ( y x. ( log ` x ) ) ) )
Theorem	dfrelog 15204	The natural logarithm function on the positive reals in terms of the real exponential function. (Contributed by Paul Chapman, 21-Apr-2008.)
|- ( log |` RR+ ) = `' ( exp |` RR )
Theorem	relogf1o 15205	The natural logarithm function maps the positive reals one-to-one onto the real numbers. (Contributed by Paul Chapman, 21-Apr-2008.)
|- ( log |` RR+ ) : RR+ -1-1-onto-> RR
Theorem	relogcl 15206	Closure of the natural logarithm function on positive reals. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( A e. RR+ -> ( log ` A ) e. RR )
Theorem	reeflog 15207	Relationship between the natural logarithm function and the exponential function. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( A e. RR+ -> ( exp ` ( log ` A ) ) = A )
Theorem	relogef 15208	Relationship between the natural logarithm function and the exponential function. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( A e. RR -> ( log ` ( exp ` A ) ) = A )
Theorem	relogeftb 15209	Relationship between the natural logarithm function and the exponential function. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( A e. RR+ /\ B e. RR ) -> ( ( log ` A ) = B <-> ( exp ` B ) = A ) )
Theorem	log1 15210	The natural logarithm of 1. One case of Property 1a of [Cohen] p. 301. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( log ` 1 ) = 0
Theorem	loge 15211	The natural logarithm of _e. One case of Property 1b of [Cohen] p. 301. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( log ` _e ) = 1
Theorem	relogoprlem 15212	Lemma for relogmul 15213 and relogdiv 15214. Remark of [Cohen] p. 301 ("The proof of Property 3 is quite similar to the proof given for Property 2"). (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( ( log ` A ) e. CC /\ ( log ` B ) e. CC ) -> ( exp ` ( ( log ` A ) F ( log ` B ) ) ) = ( ( exp ` ( log ` A ) ) G ( exp ` ( log ` B ) ) ) )   &    |- ( ( ( log ` A ) e. RR /\ ( log ` B ) e. RR ) -> ( ( log ` A ) F ( log ` B ) ) e. RR )   =>    |- ( ( A e. RR+ /\ B e. RR+ ) -> ( log ` ( A G B ) ) = ( ( log ` A ) F ( log ` B ) ) )
Theorem	relogmul 15213	The natural logarithm of the product of two positive real numbers is the sum of natural logarithms. Property 2 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( A e. RR+ /\ B e. RR+ ) -> ( log ` ( A x. B ) ) = ( ( log ` A ) + ( log ` B ) ) )
Theorem	relogdiv 15214	The natural logarithm of the quotient of two positive real numbers is the difference of natural logarithms. Exercise 72(a) and Property 3 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( A e. RR+ /\ B e. RR+ ) -> ( log ` ( A / B ) ) = ( ( log ` A ) - ( log ` B ) ) )
Theorem	reexplog 15215	Exponentiation of a positive real number to an integer power. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( A e. RR+ /\ N e. ZZ ) -> ( A ^ N ) = ( exp ` ( N x. ( log ` A ) ) ) )
Theorem	relogexp 15216	The natural logarithm of positive A raised to an integer power. Property 4 of [Cohen] p. 301-302, restricted to natural logarithms and integer powers N. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( A e. RR+ /\ N e. ZZ ) -> ( log ` ( A ^ N ) ) = ( N x. ( log ` A ) ) )
Theorem	relogiso 15217	The natural logarithm function on positive reals determines an isomorphism from the positive reals onto the reals. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( log |` RR+ ) Isom < , < ( RR+ , RR )
Theorem	logltb 15218	The natural logarithm function on positive reals is strictly monotonic. (Contributed by Steve Rodriguez, 25-Nov-2007.)
|- ( ( A e. RR+ /\ B e. RR+ ) -> ( A < B <-> ( log ` A ) < ( log ` B ) ) )
Theorem	logleb 15219	Natural logarithm preserves <_. (Contributed by Stefan O'Rear, 19-Sep-2014.)
|- ( ( A e. RR+ /\ B e. RR+ ) -> ( A <_ B <-> ( log ` A ) <_ ( log ` B ) ) )
Theorem	logrpap0b 15220	The logarithm is apart from 0 if and only if its argument is apart from 1. (Contributed by Jim Kingdon, 3-Jul-2024.)
|- ( A e. RR+ -> ( A # 1 <-> ( log ` A ) # 0 ) )
Theorem	logrpap0 15221	The logarithm is apart from 0 if its argument is apart from 1. (Contributed by Jim Kingdon, 5-Jul-2024.)
|- ( ( A e. RR+ /\ A # 1 ) -> ( log ` A ) # 0 )
Theorem	logrpap0d 15222	Deduction form of logrpap0 15221. (Contributed by Jim Kingdon, 3-Jul-2024.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> A # 1 )   =>    |- ( ph -> ( log ` A ) # 0 )
Theorem	rplogcl 15223	Closure of the logarithm function in the positive reals. (Contributed by Mario Carneiro, 21-Sep-2014.)
|- ( ( A e. RR /\ 1 < A ) -> ( log ` A ) e. RR+ )
Theorem	logge0 15224	The logarithm of a number greater than 1 is nonnegative. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ( A e. RR /\ 1 <_ A ) -> 0 <_ ( log ` A ) )
Theorem	logdivlti 15225	The log x / x function is strictly decreasing on the reals greater than _e. (Contributed by Mario Carneiro, 14-Mar-2014.)
|- ( ( ( A e. RR /\ B e. RR /\ _e <_ A ) /\ A < B ) -> ( ( log ` B ) / B ) < ( ( log ` A ) / A ) )
Theorem	relogcld 15226	Closure of the natural logarithm function. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR+ )   =>    |- ( ph -> ( log ` A ) e. RR )
Theorem	reeflogd 15227	Relationship between the natural logarithm function and the exponential function. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR+ )   =>    |- ( ph -> ( exp ` ( log ` A ) ) = A )
Theorem	relogmuld 15228	The natural logarithm of the product of two positive real numbers is the sum of natural logarithms. Property 2 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR+ )   =>    |- ( ph -> ( log ` ( A x. B ) ) = ( ( log ` A ) + ( log ` B ) ) )
Theorem	relogdivd 15229	The natural logarithm of the quotient of two positive real numbers is the difference of natural logarithms. Exercise 72(a) and Property 3 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR+ )   =>    |- ( ph -> ( log ` ( A / B ) ) = ( ( log ` A ) - ( log ` B ) ) )
Theorem	logled 15230	Natural logarithm preserves <_. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR+ )   =>    |- ( ph -> ( A <_ B <-> ( log ` A ) <_ ( log ` B ) ) )
Theorem	relogefd 15231	Relationship between the natural logarithm function and the exponential function. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR )   =>    |- ( ph -> ( log ` ( exp ` A ) ) = A )
Theorem	rplogcld 15232	Closure of the logarithm function in the positive reals. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR )   &    |- ( ph -> 1 < A )   =>    |- ( ph -> ( log ` A ) e. RR+ )
Theorem	logge0d 15233	The logarithm of a number greater than 1 is nonnegative. (Contributed by Mario Carneiro, 29-May-2016.)
|- ( ph -> A e. RR )   &    |- ( ph -> 1 <_ A )   =>    |- ( ph -> 0 <_ ( log ` A ) )
Theorem	logge0b 15234	The logarithm of a number is nonnegative iff the number is greater than or equal to 1. (Contributed by AV, 30-May-2020.)
|- ( A e. RR+ -> ( 0 <_ ( log ` A ) <-> 1 <_ A ) )
Theorem	loggt0b 15235	The logarithm of a number is positive iff the number is greater than 1. (Contributed by AV, 30-May-2020.)
|- ( A e. RR+ -> ( 0 < ( log ` A ) <-> 1 < A ) )
Theorem	logle1b 15236	The logarithm of a number is less than or equal to 1 iff the number is less than or equal to Euler's constant. (Contributed by AV, 30-May-2020.)
|- ( A e. RR+ -> ( ( log ` A ) <_ 1 <-> A <_ _e ) )
Theorem	loglt1b 15237	The logarithm of a number is less than 1 iff the number is less than Euler's constant. (Contributed by AV, 30-May-2020.)
|- ( A e. RR+ -> ( ( log ` A ) < 1 <-> A < _e ) )
Theorem	rpcxpef 15238	Value of the complex power function. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 12-Jun-2024.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( A ^c B ) = ( exp ` ( B x. ( log ` A ) ) ) )
Theorem	cxpexprp 15239	Relate the complex power function to the integer power function. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 12-Jun-2024.)
|- ( ( A e. RR+ /\ B e. ZZ ) -> ( A ^c B ) = ( A ^ B ) )
Theorem	cxpexpnn 15240	Relate the complex power function to the integer power function. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 12-Jun-2024.)
|- ( ( A e. NN /\ B e. ZZ ) -> ( A ^c B ) = ( A ^ B ) )
Theorem	logcxp 15241	Logarithm of a complex power. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. RR ) -> ( log ` ( A ^c B ) ) = ( B x. ( log ` A ) ) )
Theorem	rpcxp0 15242	Value of the complex power function when the second argument is zero. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 12-Jun-2024.)
|- ( A e. RR+ -> ( A ^c 0 ) = 1 )
Theorem	rpcxp1 15243	Value of the complex power function at one. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( A e. RR+ -> ( A ^c 1 ) = A )
Theorem	1cxp 15244	Value of the complex power function at one. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( A e. CC -> ( 1 ^c A ) = 1 )
Theorem	ecxp 15245	Write the exponential function as an exponent to the power _e. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( A e. CC -> ( _e ^c A ) = ( exp ` A ) )
Theorem	rpcncxpcl 15246	Closure of the complex power function. (Contributed by Jim Kingdon, 12-Jun-2024.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( A ^c B ) e. CC )
Theorem	rpcxpcl 15247	Positive real closure of the complex power function. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. RR ) -> ( A ^c B ) e. RR+ )
Theorem	cxpap0 15248	Complex exponentiation is apart from zero. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 12-Jun-2024.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( A ^c B ) # 0 )
Theorem	rpcxpadd 15249	Sum of exponents law for complex exponentiation. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 13-Jun-2024.)
|- ( ( A e. RR+ /\ B e. CC /\ C e. CC ) -> ( A ^c ( B + C ) ) = ( ( A ^c B ) x. ( A ^c C ) ) )
Theorem	rpcxpp1 15250	Value of a nonzero complex number raised to a complex power plus one. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( A ^c ( B + 1 ) ) = ( ( A ^c B ) x. A ) )
Theorem	rpcxpneg 15251	Value of a complex number raised to a negative power. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( A ^c -u B ) = ( 1 / ( A ^c B ) ) )
Theorem	rpcxpsub 15252	Exponent subtraction law for complex exponentiation. (Contributed by Mario Carneiro, 22-Sep-2014.)
|- ( ( A e. RR+ /\ B e. CC /\ C e. CC ) -> ( A ^c ( B - C ) ) = ( ( A ^c B ) / ( A ^c C ) ) )
Theorem	rpmulcxp 15253	Complex exponentiation of a product. Proposition 10-4.2(c) of [Gleason] p. 135. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. RR+ /\ C e. CC ) -> ( ( A x. B ) ^c C ) = ( ( A ^c C ) x. ( B ^c C ) ) )
Theorem	cxprec 15254	Complex exponentiation of a reciprocal. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( ( 1 / A ) ^c B ) = ( 1 / ( A ^c B ) ) )
Theorem	rpdivcxp 15255	Complex exponentiation of a quotient. (Contributed by Mario Carneiro, 8-Sep-2014.)
|- ( ( A e. RR+ /\ B e. RR+ /\ C e. CC ) -> ( ( A / B ) ^c C ) = ( ( A ^c C ) / ( B ^c C ) ) )
Theorem	cxpmul 15256	Product of exponents law for complex exponentiation. Proposition 10-4.2(b) of [Gleason] p. 135. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( A e. RR+ /\ B e. RR /\ C e. CC ) -> ( A ^c ( B x. C ) ) = ( ( A ^c B ) ^c C ) )
Theorem	rpcxpmul2 15257	Product of exponents law for complex exponentiation. Variation on cxpmul 15256 with more general conditions on A and B when C is a nonnegative integer. (Contributed by Mario Carneiro, 9-Aug-2014.)
|- ( ( A e. RR+ /\ B e. CC /\ C e. NN0 ) -> ( A ^c ( B x. C ) ) = ( ( A ^c B ) ^ C ) )
Theorem	rpcxproot 15258	The complex power function allows us to write n-th roots via the idiom A ^c ( 1 / N ). (Contributed by Mario Carneiro, 6-May-2015.)
|- ( ( A e. RR+ /\ N e. NN ) -> ( ( A ^c ( 1 / N ) ) ^ N ) = A )
Theorem	abscxp 15259	Absolute value of a power, when the base is real. (Contributed by Mario Carneiro, 15-Sep-2014.)
|- ( ( A e. RR+ /\ B e. CC ) -> ( abs ` ( A ^c B ) ) = ( A ^c ( Re ` B ) ) )
Theorem	cxplt 15260	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( ( A e. RR /\ 1 < A ) /\ ( B e. RR /\ C e. RR ) ) -> ( B < C <-> ( A ^c B ) < ( A ^c C ) ) )
Theorem	cxple 15261	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 2-Aug-2014.)
|- ( ( ( A e. RR /\ 1 < A ) /\ ( B e. RR /\ C e. RR ) ) -> ( B <_ C <-> ( A ^c B ) <_ ( A ^c C ) ) )
Theorem	rpcxple2 15262	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 8-Sep-2014.)
|- ( ( A e. RR+ /\ B e. RR+ /\ C e. RR+ ) -> ( A <_ B <-> ( A ^c C ) <_ ( B ^c C ) ) )
Theorem	rpcxplt2 15263	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 15-Sep-2014.)
|- ( ( A e. RR+ /\ B e. RR+ /\ C e. RR+ ) -> ( A < B <-> ( A ^c C ) < ( B ^c C ) ) )
Theorem	cxplt3 15264	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 2-May-2016.)
|- ( ( ( A e. RR+ /\ A < 1 ) /\ ( B e. RR /\ C e. RR ) ) -> ( B < C <-> ( A ^c C ) < ( A ^c B ) ) )
Theorem	cxple3 15265	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 2-May-2016.)
|- ( ( ( A e. RR+ /\ A < 1 ) /\ ( B e. RR /\ C e. RR ) ) -> ( B <_ C <-> ( A ^c C ) <_ ( A ^c B ) ) )
Theorem	rpcxpsqrt 15266	The exponential function with exponent 1 / 2 exactly matches the square root function, and thus serves as a suitable generalization to other n-th roots and irrational roots. (Contributed by Mario Carneiro, 2-Aug-2014.) (Revised by Jim Kingdon, 16-Jun-2024.)
|- ( A e. RR+ -> ( A ^c ( 1 / 2 ) ) = ( sqr ` A ) )
Theorem	logsqrt 15267	Logarithm of a square root. (Contributed by Mario Carneiro, 5-May-2016.)
|- ( A e. RR+ -> ( log ` ( sqr ` A ) ) = ( ( log ` A ) / 2 ) )
Theorem	rpcxp0d 15268	Value of the complex power function when the second argument is zero. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   =>    |- ( ph -> ( A ^c 0 ) = 1 )
Theorem	rpcxp1d 15269	Value of the complex power function at one. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   =>    |- ( ph -> ( A ^c 1 ) = A )
Theorem	1cxpd 15270	Value of the complex power function at one. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. CC )   =>    |- ( ph -> ( 1 ^c A ) = 1 )
Theorem	rpcncxpcld 15271	Closure of the complex power function. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. CC )   =>    |- ( ph -> ( A ^c B ) e. CC )
Theorem	cxpltd 15272	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR )   &    |- ( ph -> 1 < A )   &    |- ( ph -> B e. RR )   &    |- ( ph -> C e. RR )   =>    |- ( ph -> ( B < C <-> ( A ^c B ) < ( A ^c C ) ) )
Theorem	cxpled 15273	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR )   &    |- ( ph -> 1 < A )   &    |- ( ph -> B e. RR )   &    |- ( ph -> C e. RR )   =>    |- ( ph -> ( B <_ C <-> ( A ^c B ) <_ ( A ^c C ) ) )
Theorem	rpcxpsqrtth 15274	Square root theorem over the complex numbers for the complex power function. Compare with resqrtth 11215. (Contributed by AV, 23-Dec-2022.)
|- ( A e. RR+ -> ( ( sqr ` A ) ^c 2 ) = A )
Theorem	cxprecd 15275	Complex exponentiation of a reciprocal. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. CC )   =>    |- ( ph -> ( ( 1 / A ) ^c B ) = ( 1 / ( A ^c B ) ) )
Theorem	rpcxpmul2d 15276	Product of exponents law for complex exponentiation. Variation on cxpmul 15256 with more general conditions on A and B when C is a nonnegative integer. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. CC )   &    |- ( ph -> C e. NN0 )   =>    |- ( ph -> ( A ^c ( B x. C ) ) = ( ( A ^c B ) ^ C ) )
Theorem	rpcxpcld 15277	Positive real closure of the complex power function. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR )   =>    |- ( ph -> ( A ^c B ) e. RR+ )
Theorem	logcxpd 15278	Logarithm of a complex power. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR )   =>    |- ( ph -> ( log ` ( A ^c B ) ) = ( B x. ( log ` A ) ) )
Theorem	cxplt3d 15279	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR )   &    |- ( ph -> A < 1 )   &    |- ( ph -> C e. RR )   =>    |- ( ph -> ( B < C <-> ( A ^c C ) < ( A ^c B ) ) )
Theorem	cxple3d 15280	Ordering property for complex exponentiation. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR )   &    |- ( ph -> A < 1 )   &    |- ( ph -> C e. RR )   =>    |- ( ph -> ( B <_ C <-> ( A ^c C ) <_ ( A ^c B ) ) )
Theorem	cxpmuld 15281	Product of exponents law for complex exponentiation. Proposition 10-4.2(b) of [Gleason] p. 135. (Contributed by Mario Carneiro, 30-May-2016.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. RR )   &    |- ( ph -> C e. CC )   =>    |- ( ph -> ( A ^c ( B x. C ) ) = ( ( A ^c B ) ^c C ) )
Theorem	cxpcom 15282	Commutative law for real exponentiation. (Contributed by AV, 29-Dec-2022.)
|- ( ( A e. RR+ /\ B e. RR /\ C e. RR ) -> ( ( A ^c B ) ^c C ) = ( ( A ^c C ) ^c B ) )
Theorem	apcxp2 15283	Apartness and real exponentiation. (Contributed by Jim Kingdon, 10-Jul-2024.)
|- ( ( ( A e. RR+ /\ A # 1 ) /\ ( B e. RR /\ C e. RR ) ) -> ( B # C <-> ( A ^c B ) # ( A ^c C ) ) )
Theorem	rpabscxpbnd 15284	Bound on the absolute value of a complex power. (Contributed by Mario Carneiro, 15-Sep-2014.) (Revised by Jim Kingdon, 19-Jun-2024.)
|- ( ph -> A e. RR+ )   &    |- ( ph -> B e. CC )   &    |- ( ph -> 0 < ( Re ` B ) )   &    |- ( ph -> M e. RR )   &    |- ( ph -> ( abs ` A ) <_ M )   =>    |- ( ph -> ( abs ` ( A ^c B ) ) <_ ( ( M ^c ( Re ` B ) ) x. ( exp ` ( ( abs ` B ) x. pi ) ) ) )
Theorem	ltexp2 15285	Ordering law for exponentiation. (Contributed by NM, 2-Aug-2006.) (Revised by Mario Carneiro, 5-Jun-2014.)
|- ( ( ( A e. RR /\ M e. ZZ /\ N e. ZZ ) /\ 1 < A ) -> ( M < N <-> ( A ^ M ) < ( A ^ N ) ) )
Theorem	ltexp2d 15286	Ordering relationship for exponentiation. (Contributed by Mario Carneiro, 28-May-2016.)
|- ( ph -> A e. RR )   &    |- ( ph -> M e. ZZ )   &    |- ( ph -> N e. ZZ )   &    |- ( ph -> 1 < A )   =>    |- ( ph -> ( M < N <-> ( A ^ M ) < ( A ^ N ) ) )
11.2.4  Logarithms to an arbitrary base Define "log using an arbitrary base" function and then prove some of its properties. As with df-relog 15202 this is for real logarithms rather than complex logarithms. Metamath doesn't care what letters are used to represent classes. Usually classes begin with the letter "A", but here we use "B" and "X" to more clearly distinguish between "base" and "other parameter of log". There are different ways this could be defined in Metamath. The approach used here is intentionally similar to existing 2-parameter Metamath functions (operations): ( B logb X ) where B is the base and X is the argument of the logarithm function. An alternative would be to support the notational form ( ( logb ` B ) ` X ); that looks a little more like traditional notation.
Syntax	clogb 15287	Extend class notation to include the logarithm generalized to an arbitrary base.
class logb
Definition	df-logb 15288*	Define the logb operator. This is the logarithm generalized to an arbitrary base. It can be used as ( B logb X ) for "log base B of X". In the most common traditional notation, base B is a subscript of "log". The definition will only be useful where x is a positive real apart from one and where y is a positive real, so the choice of ( CC \ { 0 , 1 } ) and ( CC \ { 0 } ) is somewhat arbitrary (we adopt the definition used in set.mm). (Contributed by David A. Wheeler, 21-Jan-2017.)
|- logb = ( x e. ( CC \ { 0 , 1 } ) , y e. ( CC \ { 0 } ) |-> ( ( log ` y ) / ( log ` x ) ) )
Theorem	rplogbval 15289	Define the value of the logb function, the logarithm generalized to an arbitrary base, when used as infix. Most Metamath statements select variables in order of their use, but to make the order clearer we use "B" for base and "X" for the argument of the logarithm function here. (Contributed by David A. Wheeler, 21-Jan-2017.) (Revised by Jim Kingdon, 3-Jul-2024.)
|- ( ( B e. RR+ /\ B # 1 /\ X e. RR+ ) -> ( B logb X ) = ( ( log ` X ) / ( log ` B ) ) )
Theorem	rplogbcl 15290	General logarithm closure. (Contributed by David A. Wheeler, 17-Jul-2017.)
|- ( ( B e. RR+ /\ B # 1 /\ X e. RR+ ) -> ( B logb X ) e. RR )
Theorem	rplogbid1 15291	General logarithm is 1 when base and arg match. Property 1(a) of [Cohen4] p. 361. (Contributed by Stefan O'Rear, 19-Sep-2014.) (Revised by David A. Wheeler, 22-Jul-2017.)
|- ( ( A e. RR+ /\ A # 1 ) -> ( A logb A ) = 1 )
Theorem	rplogb1 15292	The logarithm of 1 to an arbitrary base B is 0. Property 1(b) of [Cohen4] p. 361. See log1 15210. (Contributed by Stefan O'Rear, 19-Sep-2014.) (Revised by Thierry Arnoux, 27-Sep-2017.)
|- ( ( B e. RR+ /\ B # 1 ) -> ( B logb 1 ) = 0 )
Theorem	rpelogb 15293	The general logarithm of a number to the base being Euler's constant is the natural logarithm of the number. Put another way, using _e as the base in logb is the same as log. Definition in [Cohen4] p. 352. (Contributed by David A. Wheeler, 17-Oct-2017.) (Revised by David A. Wheeler and AV, 16-Jun-2020.)
|- ( A e. RR+ -> ( _e logb A ) = ( log ` A ) )
Theorem	rplogbchbase 15294	Change of base for logarithms. Property in [Cohen4] p. 367. (Contributed by AV, 11-Jun-2020.)
|- ( ( ( A e. RR+ /\ A # 1 ) /\ ( B e. RR+ /\ B # 1 ) /\ X e. RR+ ) -> ( A logb X ) = ( ( B logb X ) / ( B logb A ) ) )
Theorem	relogbval 15295	Value of the general logarithm with integer base. (Contributed by Thierry Arnoux, 27-Sep-2017.)
|- ( ( B e. ( ZZ>= ` 2 ) /\ X e. RR+ ) -> ( B logb X ) = ( ( log ` X ) / ( log ` B ) ) )
Theorem	relogbzcl 15296	Closure of the general logarithm with integer base on positive reals. (Contributed by Thierry Arnoux, 27-Sep-2017.) (Proof shortened by AV, 9-Jun-2020.)
|- ( ( B e. ( ZZ>= ` 2 ) /\ X e. RR+ ) -> ( B logb X ) e. RR )
Theorem	rplogbreexp 15297	Power law for the general logarithm for real powers: The logarithm of a positive real number to the power of a real number is equal to the product of the exponent and the logarithm of the base of the power. Property 4 of [Cohen4] p. 361. (Contributed by AV, 9-Jun-2020.)
|- ( ( ( B e. RR+ /\ B # 1 ) /\ C e. RR+ /\ E e. RR ) -> ( B logb ( C ^c E ) ) = ( E x. ( B logb C ) ) )
Theorem	rplogbzexp 15298	Power law for the general logarithm for integer powers: The logarithm of a positive real number to the power of an integer is equal to the product of the exponent and the logarithm of the base of the power. (Contributed by Stefan O'Rear, 19-Sep-2014.) (Revised by AV, 9-Jun-2020.)
|- ( ( ( B e. RR+ /\ B # 1 ) /\ C e. RR+ /\ N e. ZZ ) -> ( B logb ( C ^ N ) ) = ( N x. ( B logb C ) ) )
Theorem	rprelogbmul 15299	The logarithm of the product of two positive real numbers is the sum of logarithms. Property 2 of [Cohen4] p. 361. (Contributed by Stefan O'Rear, 19-Sep-2014.) (Revised by AV, 29-May-2020.)
|- ( ( ( B e. RR+ /\ B # 1 ) /\ ( A e. RR+ /\ C e. RR+ ) ) -> ( B logb ( A x. C ) ) = ( ( B logb A ) + ( B logb C ) ) )
Theorem	rprelogbmulexp 15300	The logarithm of the product of a positive real and a positive real number to the power of a real number is the sum of the logarithm of the first real number and the scaled logarithm of the second real number. (Contributed by AV, 29-May-2020.)
|- ( ( ( B e. RR+ /\ B # 1 ) /\ ( A e. RR+ /\ C e. RR+ /\ E e. RR ) ) -> ( B logb ( A x. ( C ^c E ) ) ) = ( ( B logb A ) + ( E x. ( B logb C ) ) ) )