Setting functions equal to each other to cancel

[getty102]

Homework Statement

sin(3x)=3sin(x)

Homework Equations

The Attempt at a Solution

How do you solve this for x?

 

[rock.freak667]

What identity can you replace sin(3x) with? (Hint: you want to write everything in terms of sinx)

 

[getty102]

Well I came up with;
(1+2cos(2x))sinx=3sinx

but that didn't work either

 

[rock.freak667]

Well I came up with;
(1+2cos(2x))sinx=3sinx

but that didn't work either

and you can replace cos(2x) by?