Question

Question #b2380

Answer 1

`sin(x)+sin(7x)=2sin(4x)cos(3x)`

Explanation:

Using the formula

`sin(alpha)+sin(beta) = 2sin((alpha+beta)/2)cos((alpha-beta)/2)`

we have

`sin(x)+sin(7x) = 2sin((x+7x)/2)cos((x-7x)/2)`

`=2sin((8x)/2)cos(-(6x)/2)`

`=2sin(4x)cos(-3x)`

`=2sin(4x)cos(3x)`