` (1−cosA+cosB−cos(A+B))/ (1+cosA−cosB−cos(A+B))` ​ =

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

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

In any Delta A B C , prove that: (cosA)/(bcosC+c cosB)+(cosB)/(c cosA+acosC)+(cosC)/(acosB+bcosA)=(a^2+b^2+c^2)/(2a b c)

let a=cosA+cosB-cos(A+B) and b=4sin(A/2)sin(B/2)cos((A+B)/2) Then a-b is

If cosA+cosB+cosC=0, then cos3A+cos3B+cos3C is equal to

If A, B, C are the angle of a triangle and |(sinA,sinB,sinC),(cosA,cosB,cosC),(cos^(3)A,cos^(3)B,cos^(3)C)|=0 , then show that DeltaABC is an isosceles.

If sinA+sinB=a and cosA+cosB=b,then cos(A+B)

In a A B C ,if|1 1 1 1+cosA 1+cosB 1+cosC cos^2A+A cos^2B+cosB cos^2C+cosC|=0 show that A B C is an isosceles.

Prove the following identities: tan^2A-tan^2B=(cos^2B-cos^2A)/(cos^2Bcos^2A)=(sin^2A-sin^2B)/(cos^2Acos^2B) (sinA-sinB)/(cosA+cosB)+(cosA-cosB)/(sinA+sinB)=0

Using properties of determinants, show that triangle ABC is isosceles, if : |(1,1,1),(1+cosA, 1+cosB, 1+cosC),(sqrecosA+cosA, cossqrB+cosB, cossqurC+cosC)| =0