SSC CHSL 8 Jan 2017 Shift 1 Paper

Question : 65 of 100

Marks: +1, -0

If sinC + sinD =X, then the value of X is?

Solution:

We know that,

sin(x+y)=sinxcosy

+cosxsiny

--------(i)
and

sin(x-y)=sinxcosy

-cosxsiny

--------(ii)
Adding equations (i) and (ii), we get :

sin(x+y)+sin(x-y)

=2sinxcosy

-----(iii)
Let

x+y=C

and

x-y=D

⇒

x={C+D}/2

y={C-D}/2

Substituting above values in equation (iii)
⇒

sinC+sinD =2sin({C+D}/2)

cos({C-D}/2)

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