Find the exact value of : cos(2 arctan(4/3))

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asked Aug 7, 2017 231k views

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BillT · Answer 1 · 2017-08-11T03:29:58+0000

cos(2 arctan(4/3)) = cos(2 arccos(3/5)) = cos^2(arccos(3/5)) - sin^2(arccos(3/5)) = cos^2(arccos(3/5)) - sin^2(arcsin(4/5)) = (3/5)^2 - (4/5)^2 = 9/25 - 16/25 = -7/25.

Find the exact value of : cos(2 arctan(4/3))

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