Natural logarithm
Returns the natural logarithm of the given expression.
The natural logarithm is the logarithm with base e.
Syntax
ln(Expression)Examples
Calculating logarithms
Logarithms can be entered as log(number, base) or using the logarithm template 
. If the base is omitted, the logarithm is interpreted as base 10. The natural logarithm is written with ln(). The number e (Euler's number) can be typed as @e, or selected from the 
menu or symbol palette.
Simplifying logarithmic expressions
Many logarithmic expressions can be simplified simply by pressing Enter. If the expressions include variables, it is often necessary to define a domain to allow simplification. You can also try using expand and factor. These tools can be helpful, but may sometimes lead to unwanted forms, such as factorizations of base numbers.
Domain of the logarithmic function
The command domain(expression, variable) shows the values of the variable for which the expression is defined.
logbase() or