化简 cos(@-兀/2)/sin(5兀/2+@)*sin(@-2兀)*cos(2兀-@)
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![化简 cos(@-兀/2)/sin(5兀/2+@)*sin(@-2兀)*cos(2兀-@)](/uploads/image/z/1729857-57-7.jpg?t=%E5%8C%96%E7%AE%80+cos%28%40-%E5%85%80%2F2%29%2Fsin%285%E5%85%80%2F2%2B%40%29%2Asin%28%40-2%E5%85%80%29%2Acos%282%E5%85%80-%40%29)
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化简 cos(@-兀/2)/sin(5兀/2+@)*sin(@-2兀)*cos(2兀-@)
化简 cos(@-兀/2)/sin(5兀/2+@)*sin(@-2兀)*cos(2兀-@)
化简 cos(@-兀/2)/sin(5兀/2+@)*sin(@-2兀)*cos(2兀-@)
用sin(2π+a)=sina
cos(2π+a)=cosa
sin(π/2+a)=cosa
cos(a-π/2)/sin(5π/2+a)*sin(a-2π)*cos(2π-a)
=sina/sin(π/2+a)sinacosa
=sin²acosa/cosa
=sin²a
1/(cos@)^2
由诱导公式
cos(@-兀/2)/sin(5兀/2+@)*sin(@-2兀)*cos(2兀-@)
=sin@/cos@*sin@*cos@
=sin²@