1.

If (a+b+c)(b+c-a)=3bc,show that A=60°.

Answer»

(b+c+a)(b+c-a)

=(b+c)2 - a2 = 3bc

b2 + c2 - a2 = bc

(b2 + c2 - a2)/2bc  =  1/2

So,  Cos A = 1/2.        (Cosine rule)

So, A = 60



Discussion

No Comment Found

Related InterviewSolutions