Education Technology

Change Of Base

Activity Overview

Discover the change of base rule for logarithms by examining the ratio of two logarithmic functions with different bases.

Key Steps

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    In Problem 1, students compare the graphs of two logarithmic functions with different bases. They are to use the Trace feature to determine the values of the bases.

    Students then use a function table to determine the constant factor of the two functions.

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    In Problem 2, students investigate the effect of the bases on the value of c by testing different values of the bases of logarithmic functions in the spreadsheet.

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    Then students find a formula to calculate c algebraically by rewriting the general logarithmic function and using the properties of logs. They can then use the formula for c, to change the base of a logarithmic function.