已知sin a cos a =1/3求(sin a-cos a)^2的值
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已知sin a cos a =1/3求(sin a-cos a)^2的值
已知sin a cos a =1/3求(sin a-cos a)^2的值
已知sin a cos a =1/3求(sin a-cos a)^2的值
(sin a-cos a)^2
=sina^2 - 2sinacosa +cosa^2
= 1- 2sina cosa
= 1-2/3
= 1/3
(sin a-cos a)^2=sin a^2-2sin acos a+cos a^2=sin a^2+cos a^2-2/3=1/3
因为sin a^2+cos a^2=1 要记住的