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

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Answer 1 · 2018-03-07T15:28:53

$sin (- 90) = - 1$ $sin (-90) = -1$

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$sin - 90 = sin (360 - 90) = sin 270$ $sin -90 = sin (360 - 90) = sin 270$

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

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

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