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प्रश्न
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`
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उत्तर
(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)`
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