Question

prove the following identity sin(x)sin(2x)+cos(x)cos(2x)=cos(x)

Answer 1

Answer:

(2x)+vos(x)cos my answer

Answer 2

Answer:

Proved

Step-by-step explanation:

sin(x)2sin(x)cos(x)+cos(x)cos(2x)    ..sin(2x)=2sin(x)cos(x)

cos(x)[2sin^2(x)+cos(2x)]

cos(x)[2sin^2(x)+2cos^2(x)-1]        ..cos2(x)=2cos^2(x)-1

cos(x)[2(sin^2(x)+cos^2(x))-1]

cos(x)[2(1)-1]                                 ..sin^2(x)+cos^2(x)=1

=cos(x)[2-1]=cos(x)    

Hence proved.