Sin(x+P/8)sin(x-p/8)

Question

Sin(x+P/8)sin(x-p/8)

Answer 1

1/2(cos(x+pi/8-(x-pi/8))-cos(x+pi/8+x+pi/8)
1/2(cos(x+pi/8-x+pi/8)-cos(2x))
1/2(cos((pi+pi)/8-cos(2x))
1/2(cos(2pi/8)-cos(2x)
1/2(cos(pi/4)-cos(2))
1/2(sqrt2/2-cos(2x))
sqrt/4-cos2x/2