Question

Find the exact value by using a half-angle identity: sin (7pi/8)

Answer 1

sin^2(x) = (1-cos2x)/2
sin 7pi/8 = rad((1-cos 7pi/4)/2)

cos(7pi/4)= cos(pi+3pi/4) = - cos 3pi/4 = 0

sin 7pi/8 = rad(2)/2

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