Prove that: `(cos A+cos B)/(cos B-cos A)=cot((A+B)/2)cot((A-B)/2)`

(sin A-sin B)/(cos B-cos A)=cot((A+B)/(2))

(cos2B+cos2A)/(cos2B-cos2A)=cot(A+B)*cot(A-B)

Prove that (1-cos A+cos B-cos(A+B))/(1+cos A-cos B-cos(A+B))=tan((A)/(2))cot((B)/(2))

If a,b and c be in A.P. prove that cos A cot((A)/(2)),cos B cot((B)/(2)), and cos C cot((C)/(2)) are in A.P.

In Delta ABC, show that (1-cos A+cos B+cos C)/(1-cos C+cos A+cos B)=tan((A)/(2))cot((C)/(2))

In a triangle ABC, prove that (a) cos(A + B) + cos C = 0 (b) tan( (A+B)/2)= cot(C/ 2)

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)

Prove that: ((cos A+cos B)/(sin A-sin B))^(n)+((sin A+sin B)/(cos A-cos B))^(n)={2cot^(n)((A-B)/(2)),quad if niseven0,if nisodd

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

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