Find the exact value of the trigonometric function cos (9pi)/4.

Lipossig 2021-01-27 Answered
Find the exact value of the trigonometric function cos(9π)4.
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Expert Answer

Derrick
Answered 2021-01-28 Author has 94 answers
Rewriting the given trigonometric function,
cos(9π)4=cos(8π+π4)
=cos(8π4+π4)
=cos(2π+π4)
We know that (2π+θ) always lies in first quadrant and in first quadrant all trigonometric functions are positive.
So applying above rule for the given trigonometric function, we get
cos(2π+π4)=cos(π4)
=12
Hence, exact value of the given trigonometric function is 12
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Jeffrey Jordon
Answered 2021-12-14 Author has 2313 answers

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