POWER OUTLET Change-of-Base Formula Since your calculator can only calculate base 10 or natural logs, you can use this formula to convert logs other bases into base 10 or In logs so that you can use your calculator to solve them. logb a = Log a log b In a or In b Example 3: Evaluate the following using common logarithms. Be sure to close parentheses! 1. log2 7 log3 8 m. logs 4 K. Example 4 : Evaluate the following using natural logarithms : o. log2 7 n. log3 8 p. logs 4