In a `triangleABC,` prove that a cos A+b cos B+c cos C=2a sin B sin C

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

In any triangle ABC, prove that a cos A+b cos B +c cos C =(8 triangle^(2))/(abc) .

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

In a Delta ABC, prove that a ( cos B + cos C) = 2 (b + c) sin^(2)""(A)/(2)

In a triangle ABC , if cos A cos B + sin A sin B sin C = 1 , then a:b:c is equal to

Prove that sin (A+B)= sin A cos B + cos A sin B.

Prove that cos (A + B) cos C - cos (B + C) cos A = sin B sin (C - A)

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) .