tanθ=1 --> θ=k*pi+pi/4,2θ=2k*pi+pi/21.sinθ * cosθ=sin(2θ)/2 = 1/2; sin^2θ = ( 1 - cos2θ ) /2 = 1/2; cos^2θ = ( 1 + cos2θ)/2 = 1/2所以sinθcosθ\sin^2θ — 2cos^2θ=1/2 / ( 1/2 - 2 * 1/2) = -...