`(sin2A+sin2B+sin2C)/(cosA+cosB+cosC-1)=(lambda/2)cosA/2cosB/2cosC/2` then `lambda=`

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

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

(sin^2A-sin^2B)/(sinA.cosA-sinB.cosB)=....

If A+B+C= pi ,prove that :cosA+cosB-cosC=-1+4cosA/2cosB/2sinC/2.

In any A B C ,2(bc cosA+ ca cosB+ab cosC) =

If A+B+C = 180^@ then (sin 2A + sin 2B + sin 2C) / (cosA + cosB + cosC - 1) =

In a quadrilateral if sin(A+B)/2cos(A-B)/2+sin(c+D)/2cos(c-D)/2=2, then cosA/2cosB/2+cosA/2cosc/2+cosA/2 cosD/2+cosB/2 cosC/2+cosB/2 cosD/2+cosC/2 cosD/2=

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

If A+B+C=180^(@) , then (sin2A+sin2B+sin2C)/(cosA+cosB+cosC-1) is equal to

If A + B + C = 180 ^ @ then (sin 2A + sin 2B + sin 2C) / (cosA + cosB + cosC - 1) =