The logBASE( Command

Command Summary

Allows you to find the log of a number using any base you want

Command Syntax

logBASE(value,base)

Menu Location

Press:

1. ALPHA, then F2 (which is located over the WINDOW button)
2. 5 or arrow keys to move down to logBASE(

or

1. MATH
2. A or arrow keys to move down to logBASE(

Calculator Compatibility

TI-84+SE with TI-OS 2.53 MP

Token Size

2 byte

The logBASE( command is a visual upgrade to the log( command to compute logarithms in any base b. That is, the command finds the exponent that base b must be raised to obtain the given value.

This command can be used on both the home screen and while programming. If you are using CLASSIC mode, the command appears as:

logBASE(8,2)
            3

But in MATHPRINT mode, this is improved to:

log₂(8)
            3

Formulas

The log in base b can also be found using the ln( or log( commands. This can be done indirectly using the change-of-base formula:

(1)

\begin{align} \log_bx = {\ln x \over \ln b} = {\log x \over \log b} \end{align}

Or directly, using the optional second argument of log(:

logBASE(X,B

can be

log(X,B

The logBASE( command costs one extra byte compared to log(, providing only a visual improvement over its counterpart in MATHPRINT mode. The log( command is also compatible with older OS's, although its second argument is not. Both logBASE( and the second argument of log( are disabled in exam mode.

Error Conditions

• ERR:ARGUMENT when a base is not specified
• ERR:DOMAIN when trying to compute the logarithm of 0
• ERR:NONREAL ANS when trying to compute the logarithm of a negative number in Real mode

Related Commands

• log(
• ln(

.