`(1-cosA+cosB-cos(A+B))/(1+cosA-cosB-cos(A+B))=tan(A/2)cot(B/2)`

In DeltaABC, show that (1-cosA+cosB+cosC)/(1-cosC+cosA+cosB)=tan(A/2) cot (C/2).

In DeltaABC, show that (1-cosA+cosB+cosC)/(1-cosC+cosA+cosB)=tan(A/2) cot (C/2).

(a+b+c)(cosA+cosB+cosC)

cos^(2)(A-B)+cos^(2)B-2cos(A-B).cosA.cosB=?

cos^2 A + cos^2 B +cos^2 C=1+2cosA cosB cosC .

Prove the following : cos4A-cos4B = 8(cosA-cosB)(cosA+cosB)(cosA-sinB)(cosA+sinB)

Prove that ((cosA+cosB)/(sinA-sinB))^n+((sinA+sinB)/(cosA-cosB))^n=2cot^n((A-B)/2) or according as n is even or oddrespectively..

Prove that (sinA+sinB)/(cosA+cosB)=tan((A+B)/2)

Show that DeltaABC is an isosceles triangle, if the determinant Delta=|(1,1,1),(1+cosA,1+cosB,1+cosC),(cos^(2)A+cosA,cos^(2)B+cosB,cos^(2)C+cosC)|=0 .