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

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

cos^2 A + cos^2 B +cos^2 C=1+2cosA cosB cosC .

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

If A + B + C = 180^(@) , prove that sin^(2)A + sin^(2)B + sin^(2) C = 2 + 2 cos A cos B cos C

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

If A + B + C = (pi)/(2) , prove that cos 2A + cos 2B + cos 2C = 1 + 4 sin A sin B cos 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

Prove that a cos A + b cos B + c cos C = 4 R sin A sin B sin C.

Expand cos ( A + B + C). Hence prove that cos A cos B cos C = sin A sin B cos C + sin B sin C cos A + sin C sin A cos B, if A + B + C = (pi)/(2) .