Hi, I'd like to solve the following differential equation to find $\displaystyle y$ as a function of $\displaystyle x$ (in fact I know what the answer should be due to the context, but I have no idea how to go about actually solving it). Any ideas would be appreciated!

$\displaystyle 1 + \left(\frac{\text{d}y}{\text{d}x}\right)^2 = \frac{y^2}{c^2}$,

where $\displaystyle c$ is a constant.