Logarithms


We consider logarithms with three different bases:

base e (natural logarithms),
base 10, and
base b other than e or 10, where 0 < b and b 1.

Recall that the domain of a logarithm function consists of all real numbers x > 0.

Press MENU 1 to select the RUN-MAT screen.

Base e

Simply use the ln (natural logarithm) key. For example, to calculate ln(17), press

ln 1 7 ) EXE

Base 10

Simply use the log (common logarithm) key. For example, to calculate log(17), press

log 1 7 ) EXE

Other Bases

For logarithmic bases other than e or 10, one must apply the change of base formula to convert to base e:

Hence, to determine log5(17), note that log5(17) = ln(17)/ln(5). Here, log5(17) 1.76.