if ` ( cos A + cos B )/( sin A + sin B ) = k ( (sin A - sin B)/ ( cos A- cos B))` then k is

(sin(A - B))/(cos A cos B) + (sin (B - C))/( cos B cos C) + (sin(C - A))/(cos C cos A) is

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) .

In a Delta ABC , 2 sinA cos B + 2 sin B cos C + 2 sin cos A = sin A + sin B + sin C, then Delta ABC is

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

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

If sin A + cos A =m then sin ^6 A + cos ^6 A is

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

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

Prove that (sin (4A - 2B) + sin (4B - 2A))/(cos (4A - 2B) + cos (4B - 2A)) = tan (A + B)