∵sinα-cosα=-3/5且(sinα)^2 (cosα)^2=1 ∴sinα-cosα=-3/5=(sinα)^2-(cosα)^2 两式分别作和和差可以得到：(sinα)^2=1/5 (cosα)^2=4/5 又3π/2＜α＜2π,可得sinα=-1/根下5 cosα=2/根下5 由半角公式sin^2...