# Chapter 2 - Acute Angles and Right Triangles - Section 2.1 Trigonometric Functions of Acute Angles - 2.1 Exercises: 31

$\theta$ = 40$^{\circ}$

#### Work Step by Step

$\tan$ $\theta$ = $\cot$ ($\theta$ + 10$^{\circ}$) According to Cofunction Identities $\tan$ $\theta$ = $\cot$ ($\theta$ + 10$^{\circ}$) is true only if the sum of the angles is 90$^{\circ}$. Therefore: $\theta$ + ($\theta$ + 10$^{\circ}$) = 90$^{\circ}$ 2$\theta$ + 10$^{\circ}$ = 90$^{\circ}$ 2$\theta$ = 80$^{\circ}$ $\theta$ = 40$^{\circ}$

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