作业帮sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证,
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![sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证,](/uploads/image/z/2758530-66-0.jpg?t=sin%282a%29%5Bcot%28a%2F2%29-tan%28a%2F2%29%5D%3D4cos%5E2%28a%29%E6%B1%82%E8%AF%81%2C)
sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证,
sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证,
sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证,
sin(2a)[cot(a/2)-tan(a/2)]
=sin(2a)*[cos(a/2)/sin(a/2) - sin(a/2)/cos(a/2)]
=2sina*cosa*[cos²(a/2) - sin²(a/2)]/[sin(a/2)*cos(a/2)]
=4sin(a/2)*cos(a/2)*cosa*cosa/[sin(a/2)*cos(a/2)]
=4cos²(a)
所以等式得证!