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Given $costheta=4/5$ and $0<theta<pi/2$ , how do you find $cos 2theta$ ?

1 Answer

Jul 20, 2016

$cos2theta=2cos^2theta-1=2*16/25-1=7/25$ .

Explanation:

$cos2theta=2cos^2theta-1=2*16/25-1=7/25$ .

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