`cos(A + B) cos (A-B) =`

Value of cos^2(A - B) + cos^2 B - 2 cos (A-B) cos Acos B is:

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

cos (B+C-A)-cos(C+A-B)+cos(A+B-C)- cos (A+B+C)=

If none of A,B, A+B is an integral multiple of pi , then prove that (1- cos A+ cos B- cos (A+B))/(1+ cos A- cos B - cos (A+B))=tan.(A)/(2) cot. (B)/(2)

cos^(2) (A-B)+cos^(2)B-2cos(A-B) cos A cos B =

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

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

Prove that : (sin A - sin B)/ (cos A + cos B) + (cos A - cos B)/ (sin A + sin B) = 0

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