How do you find the exact value of cos^-1(cos(-pi/4))cos−1(cos(−π4))?

1 Answer
Binayaka C.
Feb 2, 2017

cos^-1 (cos(-pi/4)) =pi/4cos−1(cos(−π4))=π4

Explanation:

pi=180^0 :. pi/4= 180/4=45^0

cos^-1 (cos(-pi/4)) = cos^-1 (cos(-45)) = cos^-1 (cos(45)) [since cos(-theta)= cos theta]. Let cos^-1 (cos 45) = theta :.cos theta= cos 45 :. theta = 45^0= pi/4 :. cos^-1 (cos(-pi/4)) =45^0=pi/4 [Ans]

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