# Chapter 6 - Review Questions - Page 501: 58

$sin(-420°)=-\frac{\sqrt 3}{2}$ $cos(-420°)=\frac{1}{2}$ $tan(-420°)=-\sqrt 3$

#### Work Step by Step

Let $θ'$ be the reference angle. We must have that $0°\leqθ'\lt360°$ $θ'=θ+n·360°$, where $n$ is an integer. $θ'=-420°+2·360°=300°$ $sin(-420°)=sin~300°=-\frac{\sqrt 3}{2}$ $cos(-420°)=cos~300°=\frac{1}{2}$ $tan(-420°)=tan~300°=-\sqrt 3$

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