# Chapter 5 - Trigonometric Functions - Section 5.3 Properties of the Trigonometric Functions - 5.3 Assess Your Understanding - Page 418: 65

$-1$

#### Work Step by Step

The sine is an odd function so $\sin{(-\theta)} = - \sin{\theta}$ Thus, $\sin{(-90^{\circ})} =- \sin{(90^{\circ})} = \boxed{-1}$

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