simplify/ln
simplify expressions involving logarithms
Calling Sequence
Parameters
Description
Examples
simplify(expr, ln)
expr
-
any expression
ln
literal name; ln
The simplify/ln function is used to simplify logarithmic expressions. It applies the following simplifications whenever it can determine that the appropriate conditions hold:
Simplification
Provided
ln⁡ab ==> b⁢ln⁡a
signum⁡a=1 and b is real
ln⁡ab ==> b⁢ln⁡−a
signum⁡a=−1 and b is even
signum⁡a=−1 and b is odd
ln⁡ab ==> b⁢ln⁡a22
a is real and b is even
a is real and b is odd
ln⁡x⁢y ==> ln⁡x+ln⁡y
0<x and signum⁡y is unknown
ln⁡x⁢y ==> ln⁡−x+ln⁡−y
signum⁡x=−1
ln⁡x⁢y ==> ln⁡−x+ln⁡y+I⁢π
signum⁡x=−1 and signum⁡y=1
ln⁡ⅇx ==> x
x is real
ln⁡LambertW⁡x ==> ln⁡x−LambertW⁡x
In the case of an integer argument to ln, the integer is factored and the logarithm is returned as a sum of logarithms.
In the case of a sum of terms as the argument to ln, the integer content of the sum is factored out and the logarithm is returned as a sum of two logarithms.
Making the appropriate assumptions on the names in the expression to be simplified (see assume) provides simplify with enough information to apply the above identities correctly.
It is inappropriate to apply the above identities in these cases since nothing is known about n, x, and y:
simplify⁡ln⁡x3,ln
ln⁡x3
simplify⁡ln⁡x⁢y
ln⁡x⁢y
simplify⁡ln⁡exp⁡x,ln
ln⁡ⅇx
simplify⁡ln⁡yn,ln
ln⁡yn
However, by making appropriate assumptions on the variables, enough information is provided to correctly apply the identities:
assume⁡n,even
assume⁡x,real
assume⁡y<0
ln⁡x~3
ln⁡−y~+ln⁡−x~
simplify⁡ln⁡exp⁡x
x~
simplify⁡ln⁡y3,ln
3⁢ln⁡−y~+I⁢π
n~⁢ln⁡−y~
Simplifications involving integer factors:
simplify⁡ln⁡−40⁢a+15⁢b,ln
ln⁡5+ln⁡−8⁢a+3⁢b
simplify⁡ln⁡345366,ln
ln⁡2+2⁢ln⁡3+ln⁡7+ln⁡2741
See Also
assume
combine
simplify
Download Help Document