यदि `A+B+C=pi` तो सिद्ध करे कि
`cos^(2)A+ cos^(2)B+ 2 cos A* cos B * cos C= sin^(2)C`

If : A+B+C=pi, "then" : 1-cos^(2) A-cos^(2)B-cos^(2)C= A) 2 cos A * cos B * cos C B) 2 sin A * cos B * cos C C) 2 cos A * sin B * cos C D) 2 cos A * cos B * sin C

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

cos2B + cos2A-cos2C = 1-4sin A sin B cos C

If A + B + C =pi , prove that : cos 2A + cos 2B + cos 2C = -1-4 cos A cos B cos C .

If A+B+C=pi , prove that cos 2A +cos 2B +cos 2C=-1-4cos A cos Bcos C.

If A+B+C=pi , prove that cos 2A +cos 2B +cos 2C=-1-4cos A cos Bcos C.

If A+B+C=2 pi, then prove that cos^(2)B+cos^(2)C-sin^(2)A=2cos A cos B cos C

If A+B+C=pi , then prove the following. cos^2A+cos^2B+2cosA cdot cosB cdot cos C=sin^2 C