若sin(x-pai/4)=3/5,则sin2x的值为___

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若sin(x-pai/4)=3/5,则sin2x的值为___

sin(x-pai/4)
=sinxcos(pai/4)-cosxsin(pai/4)
=根号2/2(sinx-cosx)
=3/5
两边平方
1/2(sinx^2-2sinxcosx+cosx^2)
=1/2(1-2sinxcosx)
=1/2(1-sin2x)
=9/25
则sin2x=7/25