∵sin2θ=3/5，0＜2θ＜90°∴sinθ+cosθ=√(sin^2+cos^2+sin2θ)=√1+sin2θ=2√10/5同理得sinθ-cosθ=√10/5原式=cosθ-sinθ/cosθ+sinθ=1-√10/20
