" iii) "cos2A+cos2B+cos2C=1-4sin A sin B sin C

If A+B+C=(3pi)/(2), prove that cos 2A+ cos 2B+ cos 2C=1-4 sin A sin B sin C .

If A+B+C=pi/2 prove the following (i) sin 2A+sin 2B +sin 2C=4 cos A cos B cos C (ii) cos 2A +cos 2B+cos 2C=1+4 sin A sin B sin C.

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

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

If A+B+C=(3pi)/(2) , then show that cos 2A+cos 2B+cos 2C=1-4 sin A sin B sin C .

If A+B+C=(3pi)/(2) , then show that cos 2A+cos 2B+cos 2C=1-4 sin A sin B sin C .

If A+B+C=(3pi)/(2) , then show that cos 2A+cos 2B+cos 2C=1-4 sin A sin B sin C .

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

If A+B+C=(3 pi)/(2), then cos2A+cos2B+cos2C is equal to (i) 1-4cos A cos B cos C( is 4sin A sin B sin C (iii) 1+2cos A cos B cos C(iv)1-4sin A sin B sin C