IF A,B,C are angles in the triangle, then prove that
`cosA+cosB-cosC=-1+4cos""A/2.cos""B/2.sin""C/2`

If A,B,C are angles in a triangle , then prove that cosA+cosB+cosC=1+4sin. (A)/(2)sin. (B)/(2) sin. (C)/(2)

IF A,B,C are angles of a triangle , Prove that cos2A+cos 2B+cos 2C=-4cosAcosBcosC-1

If A, B, C are angles of a triangle , prove that cos 2A - cos 2B + cos 2C =1 -4 sin A cos B sin C

If A, B, C are angles in a triangle , then prove that cos^(2)A+cos^(2)B-cos^(2)C=1-2sin Asin Bcos C.

IF A+B+C=2S, then prove that cos(S-A)+cos(S-B)+cosC=-1+4cos""(S-A)/2cos""(S-B)/2cos""C/2 .

If A+B+C=0 then show that 1+cosA+cosB+cosC=4"cos"A/2"cos"B/2"cos"C/2

If A, B, C are angles of a triangle , prove that cos 2A+cos 2B -cos 2C=1-4 sin A sin B cos C

If A , B , C are angles in a triangle , then prove that sin A + sin B + sin C =4 cos. (A)/(2) cos . (B)/(2) cos .(C)/(2)

If A, B, C are angles of a triangle , prove that sin 2A+sin 2B-sin 2C=4cos Acos B sin C

If A+B+C=0^(@) then prove that sinA+sinB-sinC=-4"cos"A/2"cos"B/2"sin"C/2