tan(x/2)*cos(x/2)平方*2怎样算出等于sinx?
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tan(x/2)*cos(x/2)平方*2怎样算出等于sinx?
我知道tan(x/2)*cos(x/2)是等于sin(x/2),但分母上的cos是有个平方的,怎么也是等于sin(x/2)呢?
我知道tan(x/2)*cos(x/2)是等于sin(x/2),但分母上的cos是有个平方的,怎么也是等于sin(x/2)呢?
2*tan(x/2)*(cos(x/2))^2
=2*[sin(x/2)/cos(x/2)]*[cos(x/2)*cos(x/2)]
=2sin(x/2)*cos(x/2)
=sin[2*(x/2)]
=sinx
=2*[sin(x/2)/cos(x/2)]*[cos(x/2)*cos(x/2)]
=2sin(x/2)*cos(x/2)
=sin[2*(x/2)]
=sinx
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