# How do you find the exact value of sin(-90)?

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#### Explanation

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#### Explanation:

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Mar 7, 2018

$\sin \left(- 90\right) = - 1$

#### Explanation:

$\sin - 90 = \sin \left(360 - 90\right) = \sin 270$

Angle ${270}^{\circ}$ is third quadrant, where only tan and cot are positive.

Hence $\sin 270 = \sin \left(180 + 90\right) = - \sin 90 = - 1$

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