Question

find the value of trigonometry function . cot(-15π/4).

Answer 1

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For any angles,

$0°=360°= 2\pi = 4\pi= 2\pi\times n \\\\where\; :\: n=1,2,3,...$

Now,
$= > \cot( - \frac{15\pi}{4} ) \\ \\ = \cot(0 - \frac{15\pi}{4} ) \\ \\ = \cot(4\pi - \frac{15\pi}{4} ) \\ \\ = \cot( \frac{\pi}{4} ) = 1$
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