Show that : `cos A+ cosB + cosC+ cos(A+B+C) = 4cos""(B+C)/(2)cos""(C+A)/(2)cos""(A+B)/(2)`.

In a DeltaABC, cos""(A)/(2)cos""(B)/(2)cos""C/(2) is

If A+B+C+D=2pi , show that : cosA-cosB+cosC-cosD=4sin( (A+B)/(2)) sin( (A+D)/(2)) cos( (A+C)/(2)) .

Prove that : (sin 2A+sin 2B + sin 2C)/(cos A + cos B + cos C-1) = 8 cos(A/2) cos( B/2) cos( C/2)

If A+B+C+D = 2pi , prove that : cosA +cosB+cosC+cosD=4 cos, (A+B)/2 cos, (B+C)/(2) cos, (C+A)/2

If A+B+C=pi , prove that : cosA + cosB-cosC=4cos(A/2) cos(B/2) sin(C/2) -1

If A + B + C = pi , then show that sin (A + B + C)/( 2) = sin(A / 2) * cos "" (B + C)/( 2) + sin "" (B + C)/( 2) * cos "" (A) / (2)

Prove that (cos C + cos A)/(c + a) + (cos B)/(b) = (1)/(b)

In any DeltaABC , prove that : (cos A)/(b cos C + c cos B) + (cos B)/(c cos A + a cos C) + (cos C)/(a cos B + b cos A) = (a^2 + b^2 + c^2)/(2abc)

If A+B+C=180^0 , prove that : cos^2 (A/2) + cos^2 (B/2) - cos^2 (C/2) = 2cos (A/2) cos (B/2) sin (C/2)

Show that, 4 R r cos ""A/2cos ""B/2 cos ""C/2 =Delta