[cos2A-cos2B-cos2C=-1+4cos A sin B sin C],[L*H*S=cos2 theta-cos2B-cos2C]

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

Theorem 2:cos2A+cos2B+cos2C=-1-4cos A cos B cos C

cos2a-cos2b + cos2c = 1-4sin a cos b sin c

If A+B+C=180^(@) then cos2A+cos2B+cos2C=1-4cos A cos B cos C 2.If A+B+C=0 then cos A+cos B+cos C=-1+4(cos A)/(2)(cos B)/(2)(cos C)/(2)

If A+B+C=(3 pi)/(2), then cos2A+cos2B+cos2C is equal to a.1-4cos A cos B cos C b.4sin A sin B sin C c.1+2cos A cos B cos Cd.1-4sin A sin B sin 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

If A+B+C=(3pi)/2 . Then cos 2A +cos 2B+cos2C is equal to ................. A) 1-4 cos A cos B cos C B) 4 sin A sin B sin C C) 1+2 cos A cos B cos C D) 1-4 sin A sin B sin C

If A+B+C=(3 pi)/(2), then cos2A+cos2B+cos2C is equal to (A)1-4cos A cos B cos C(B)4sin A sin B sin C(C)1+42cos A cos B cos C(D)1-4sin A sin B sin C