Remember that with exponential and logarithmic functions, there is one very special base: {{MATH_33}} This is an irrational number that you will see frequently. The exponential with base {{MATH_34}}, {{MATH_35}} is often called the `natural exponential' function. For the logarithm with base {{MATH_36}}, we have a special notation, {{MATH_37}} is `natural logarithm' function.