Asked by Amanda
cos(2tan^-1(15/8))
Answers
Answered by
Steve
If θ = tan^-1(15/8)
sinθ = 15/17
cosθ = 8/17
now use the double angle formula
cos2θ = 2cos^2 θ - 1 = 2(64/289)-1 = -161/289
cos2θ = 1 - 2sin^2 θ = 1-450/289 = -161/289
sinθ = 15/17
cosθ = 8/17
now use the double angle formula
cos2θ = 2cos^2 θ - 1 = 2(64/289)-1 = -161/289
cos2θ = 1 - 2sin^2 θ = 1-450/289 = -161/289
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