已知sin a cos a =1/3求(sin a-cos a)^2的值
问题描述:
已知sin a cos a =1/3求(sin a-cos a)^2的值
答
(sin a-cos a)^2
=sina^2 - 2sinacosa +cosa^2
= 1- 2sina cosa
= 1-2/3
= 1/3