Question

prove that Cos pi by 4 plus X + Cos pi by 4 minus X equal to root 2 cos x ​

Answer 1

hii mate;

to prove here

cos( π /4+x)+cos (π/4 - x)=√2 cos x

let

L.H.S.

= cos( π /4+x)+cos (π/4 - x)

USING FORMULA

COS (A-B) +COS(A+ B)= 2cos A cos B

so,

=2cos π/4 cos A. [cos π/4)=1/√2]

=2×1/√2 cosA

= √2 cosA

=R.H.S.

i hopes its help's u.

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@abhi