I have these two equations
$u = \frac{2x}{x^2 + y^2} \\ v = \frac{-2y}{x^2 + y^2}$
And I need to put $x$ in terms of $u$ and $v$. If I take polar co-ordinates and plug them in I get(in the case of $u$), because
(rcos(theta))^2 + (rsin(theta))^2 = 1
$u = 2r\cos(\theta)$
Can I simply change that back to
$u = 2x$
?