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

Lipossig

Lipossig

Answered question

2021-01-27

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

Answer & Explanation

Derrick

Derrick

Skilled2021-01-28Added 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
Jeffrey Jordon

Jeffrey Jordon

Expert2021-12-14Added 2605 answers

Answer is given below (on video)

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