Question

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

Prove it​

Answer 1

$\mathfrak{\huge{\pink{\underline{\underline{AnswEr :}}}}}$

Let, a = k sinA, b = k sinB, c = k sinC

RHS

⇒b-c/a cos A/2

⇒ (ksinB - ksinC/k sinA )cos A/2

⇒ {[2 cos B+C/2 Sin B-C/2]/ Sin A} cos A/2

⇒[2* Sin B-C/2 cos (pi/2-A/2) .cos A/2] / sinA

⇒ [SinA* sinB-C/2] / sinA

⇒ Sin B-C/2 = LHS

Answer 2

Answer:

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