cos2x/sin(x+45°)=1/2 那么sin2x等于多少
问题描述：
cos2x/sin(x+45°)=1/2 那么sin2x等于多少
答
cos2x/sin(x+45°) =1/2 [cos^2x-sin^2x] /(sinxcos45°+cosxsin45°) = 1/2[(cosx+xinx)(cosx-sinx)] / [√2/2(cosx+sinx)] = 1/2cosx-sinx = √2/4(cosx-sinx)^2 = 1/4cos^2x-2cossinx+sin^2x = 1/41-sin2x = 1/4s...