Posted by sandeep on .
cos^2xsinxcosx1/2=o

math 
Steve,
dropping the x's for brevity,
2cos^2  1 = 2sin cos
4cos^4  4cos^2 + 1 = 4sin^2 cos^2
4cos^4  4cos^2 + 1 = 4(1cos^2) cos^2
4cos^4  4cos^2 + 1 = 4cos^2  4cos^4
8cos^4  8cos^2 + 1 = 0
cos^2 = 1/4 (2 ± √2)
x = kπ/2 ± π/8 for integer k