If we have

> 
> $$\arcsin\left(2x\sqrt{1-x^2}\right) = 2 \arcsin x$$
> 
> 
> 

Then, what will be the set of $x$ for which this equation is true?

I tried to solve it by putting $x = \sin a$ or $\cos a$ but got no result.

I am totally stuck on how to do it.