已知sinαcosα=1∕8且π∕4<α<π∕2,则cosα-sinα=
问题描述:
已知sinαcosα=1∕8且π∕4<α<π∕2,则cosα-sinα=
答
(cosa-sina)²
=sin²a-2sinacosa+cos²a
=1- 2/8
=3/4
又
π∕4<α<π∕2
cosa
cosα-sinα=-√3/2