## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\approx 2.771$
We wish to find the value of the given term $\log_{3} (21)$ by using a calculator. First, we apply the Change-of-Base Formula: $\log_a b =\dfrac{\log b}{\log a}$ The expression can be simplified as: $\log_{10} (21)=\dfrac{\log (21)}{\log (3)} = 2.771243749 \approx 2.771$