三角形ABC 证明sin(A/2)*sin(B/2)*sin(C/2)
问题描述：
三角形ABC 证明sin(A/2)*sin(B/2)*sin(C/2)
答
证明：sin(A/2)*sin(B/2)*sin(C/2)=sin(A/2)*sin(B/2)*sin[(π-A-B)/2]=sin(A/2)*sin(B/2)*cos[(A+B)/2]=-0.5{cos[(A+B)/2]-cos[(A-B)/2]}*cos[(A+B)/2]=-0.5{cos[(A+B)/2]}^2+0.5cos[(A-B)/2]cos[(A+B)/2]可以看成...