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
tan(x/2)*cos(x/2)平方*2怎样算出等于sinx?
2个回答
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