若sin2α=1/4,π/4
问题描述：
若sin2α=1/4,π/4
答
(cosα-sinα)^2=cos^2α+sin^2-2sinαcosα=1-1/4=3/4因为π/4
答
2*sin a*cos a=1/4;
(sin a)^2+(cos a)^2=1;
联立,解得.