If `A+B+C=0` , then the value of `sin^2A+cosC(cosAcosB-cosC)+cosB(cosAcosC-cosB)` is equal to: `-1` (b) 0 (c) 1 (d) none of these

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

cosA+cosB+cosC is equal to (A) r/R (B) R/r (C) 1 (D) 1+r/R

If A+B+C=pi, then the value of |[sin(A+B+C),sin(A+C),cosC],[-sinB,0,tanC],[cos(A+B),tan(B+C),0]|is equal to (a)0 (b) 1 (c) 2sinBtanAcosC (d) none of these

If A+B+C=pi, then the value of |[sin(A+B+C),sin(A+C),cosC],[-sinB,0,tanC],[cos(A+B),tan(B+C),0]| is equal to (a) 0 (b) 1 (c) 2sinBtanAcosC (d) none of these

a(cosC-cosB)=2(b-c)cos^2A/2

In a /_\ABC , cosec A[sinB.cosC+cosB.sinC]= (A) c/a (B) a/c (C) 1 (D) none of these

In a /_\ABC , cosec A[sinB.cosC+cosB.sinC]= (A) c/a (B) a/c (C) 1 (D) none of these

If A+B+C=pi,then show that Abs((-1,cosC,cosB),(cosC,-1,cosA),(cosB,cosA,-1))=0

If A+B+C=0, then prove that Det[[1,cosC,cosB],[cosC,1,cosA],[cosB,cosA,1]]=0