cos（α+π/4）=√2/2(cosα-sinα)=-3/5,sinα-cosα=3√2/5,sin^2α=cos^2α-+6√2/5cosα+18/252cos^2α+6√2/5cosα-7/25=0=(√2cosα-1/5)(√2cosα+7/5),cosα=√2/10 （或-√72/10舍去）sinα=7√2/10sin(β+...