Please help me with a math problem

[Davros]

It's been around 10 years since I've done any serious maths, so I'm struggling with this.

I have an equation y = f(x) which looks like

y = c ( sin(2x) + x )

I want to re-arrange this to get the reverse, i.e. an equation for x given a value for y. So I would have x = f'(y)

But I can't seperate the x's all onto one side. The nearest I can get is:

x = 0.5 * asin( (y/c) - x )

but this leaves me with x buried on the right hand side.

Help please!

[red_baron]

this is all i can get

[BMJ]

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