If A+B+C =`pi`show that `cos^2 (A/2)-cos^2 (B/2)-cos^2 (C/2)=-2sin(A/2)cos(B/2)cos(C/2)`

Prove that cosA -cosB -cosC =1-4sin(A/2)cos(B/2)cos(C/2) ,if A+B+C= pi

In A B C Prove that cos^2A/2+cos^2B/2+cos^2C/2lt=9/4dot In cos^2A/2+cos^2B/2+cos^2C/2=y(x^2+1/(x^2)) then find the maximum value of ydot

IF A + B + C = pi then cos ^2 A + cos^2 B + cos^2 C=

If A+B+C=180^0 , prove that : cos^2, A/2 + cos^2, B/2 - cos^2, C/2 = 2cos, A/2 cos, B/2 sin, C/2

If A+B+C=pi prove that cos^(2) A+cos^(2) B+cos^(2) C=1 - 2cos A cos B cos C .

In A B C , prove that cos e c A/2+cos e c B/2+cos e c C/2geq6.

Prove that cos (A + B) cos (A - B) = cos^(2) B - sin^(2) A

Prove that cos (A + B) cos (A - B) = cos^(2) A - sin^(2) B = cos^(2) B- sin^(2) A