` I f ` cos A + cos B + cos C ` = ` 0 `t h e n ` cos 3 A + cos 3 B + cos 3 C ` = ` λ `( cos A cos B cos C)` t h e n ` λ `

In any DeltaABC , a cos A +b cos B + c cos C =

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

In a triangle ABC, cos A+cos B+cos C=

If three angles A, B, C are such that cos A+ cos B + cos C = 0 and if lambda cos A cos B cos C = cos 3A + cos 3B + cos 3C , then value of lambda is :

Prove that: cos(A+B+C)+cos(A-B+C)+cos(A+B-C)+cos(-A+B+C)=4cos A\ cos B\ cos C

a^2(cos^2B-cos^2C)+b^2(cos^2C-cos^2A)+c^2(cos^2A-cos^2B)=0 .

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 cos 3A +cos 3B+cos 3C=1 then one of the angles of the triangle ABC is

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

If A+B+C=180^(@), " then " (cosAcosC+cos(A+B)cos(B+C))/(cosAsinC-sin(A+B)cos(B+C)) simplifies to :