Question 53

If $$(A + B + C) = 90$$°, then what is the value of $$\sin \left(\frac{A}{2}\right) \sin \left[\frac{(180 — B — C)}{2}\right] + \cos \left(\frac{A}{2}\right) \sin \frac{(B + C)}{2}$$?

Solution

We have :
A+B+C =90 
Now (180-B-C)/2 = 90-(B-C)/2
Now sin (180-B-C)/2)= sin (90-(B+C)/2 )= cos (B+C)/2
So we get the expression as
$$\sin\ \frac{A}{2}\cos\ \frac{B+C}{2}+\cos\ \frac{A}{2}\sin\ \frac{B+C}{2}=\sin\ \left(\frac{A+B+C}{2}\right)\ =\sin\ 45\ =\ \frac{1}{\sqrt{\ 2}}$$


Create a FREE account and get:

  • Free SSC Study Material - 18000 Questions
  • 230+ SSC previous papers with solutions PDF
  • 100+ SSC Online Tests for Free

cracku

Boost your Prep!

Download App