Question

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Answer 1

In a triangle sum of angles is 180°

i.e., a+b+c=180°

Require to prove:-

sin (b+c/2)=cos (a/2)

Proof:-

$l.h.s = \sin(\frac{b + c}{2} ) \\ = \sin( \frac{180 - a}{2} ) \\ = \sin(90 - \frac{a}{2} ) \\ \cos( \frac{a}{2} ) \\ = r.h .s$

Hence proved

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