# Chapter 14 Trigonometric Graphs, Identities, and Equations - 14.6 Apply Sum and Difference Formulas - 14.6 Exercises - Skill Practice - Page 952: 3

$\sqrt3-2$

#### Work Step by Step

Using the given formula and the known values: $\tan (-15^\circ)=\frac{\tan 45^\circ-\tan 60^\circ}{1+\tan 45^\circ\tan 60}=\frac{1-\sqrt3}{1+1\sqrt3}=\sqrt3-2$

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