已知a为锐角,且cos(a+四分之派)=3/5,求sina=?
人气:260 ℃ 时间:2020-02-03 10:15:57
解答
因为cos(α+π/4)=3/5,所以sin(α+π/4)=4/5.
所以sinα=sin[(α+π/4)-π/4]
=sin(α+π/4)cos(π/4)-cos(α+π/4)sin(π/4)
=√2/2*(4/5-3/5)
=√2/10.
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