Question

In Δ ABC, if a = 13, b = 14 and c = 15, then sin (A/2)= _______.

(A) `1/5`

(B) `sqrt(1/5)`

(C) `4/5`

(D) `2/5`

Answer 1

(B) `sqrt(1/5)`

`s=(a+b+c)/2=(13+14+15)/2=21`

`sin(A/2)=sqrt(((s-b)(s-c))/(bc))=sqrt(((21-14)(21-15))/(14xx15))=sqrt(1/5)`