" If "cos A=m cos B," then- "

If quad cos A=m cos B, then (cot(A+B))/(2)(cos(B-A))/(2)a*(m-1)/(m+1) b.(m+2)/(m-2) c.(m+1)/(m-1)d .none of these

If sin A + sin B = I, cos A-cos B = m then cos (AB) =

If three angles A, B, C are such that cos A+ cos B + cos C = 0 and if lambda cos A cos B cos C = cos 3A + cos 3B + cos 3C , then value of lambda is :

If sin A+sin B=a and cos A+cos B=b then cos (A+B)=

If cos A+ cos B + cos C =0 then cos 3A+ cos 3B + cos 3X

If (cos A)/(cos B)=m and (cos A)/(sin B)=n then prove that (m^(2)+n^(2))cos^(2)B=n^(2)

If : A+B+C=pi, "then" : 1-cos^(2) A-cos^(2)B-cos^(2)C= A) 2 cos A * cos B * cos C B) 2 sin A * cos B * cos C C) 2 cos A * sin B * cos C D) 2 cos A * cos B * sin C