Prove that `(b+c)cosA+(c+a)cosB+(a+b)cosC=2sdot`

In triangleABC, (b+c)cosA+(c+a)cosB+(a+b)cosC=

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

If A+B+C=180^0 , prove that : cos^2 A + cos^2 B + cos^2 C + 2cosA cosB cosC=1 .

In triangle ABC, prove that (b/c+c/b) cosA +(a/b+b/a) cos C+(a/c+c/a)cosB=3

In DeltaABC , prove that: (c-bcosA)/(b-ccosA)=(cosB)/(cosC)

With usual notation, if in a DeltaABC(b+c)/(11)=(c+a)/(12)=(a+b)/(13) , then prove that (cosA)/(7)=(cosB)/(19)=(cosC)/(25)

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

In DeltaABC , prove that: sin(A+B/2).cosB/2=(c+a)/(a+b)cosC/2.cos(A-B)/(2)

If A+B+C=pi , prove that : cosA sinB sinC +cosB sinC sinA+cosC sinA sinB=1+cosA cosB cosC .

In a DeltaABC , (b+c)(bc)cosA+(a+c)(ac)cosB+(a+b)(ab)cosC is