化简sina(1+tga*tan(a/2)
问题描述：
化简sina(1+tga*tan(a/2)
答
sina[1+tana*tan(a/2)]
=sina[cosacos(a/2)+sinasin(a/2)]/[sinasin(a/2)]
=sinacos(a-a/2)/[sinasin(a/2)]
=cot(a/2)
答
原式
=sina{1+[sina*sin(a/2)]/[cosa*cos(a/2)]}
=sina{1+[2sin(a/2)cos(a/2)*sin(a/2)]/cosa*cos(a/2)}
=sina[1+2sin(a/2)^2/cosa]
=sina{[1+2sin(a/2)^2-2sin(a/2)^2]/cosa}
=tana