# Parametric equation of a cone

I usually use the following parametric equation to find the surface area of a regular cone $z=\sqrt{x^2+y^2}$: $$x=r\cos\theta$$ $$y=r\sin\theta$$ $$z=r$$

And make $0\leq r \leq 2\pi$, $0 \leq \theta \leq 2\pi$.

I've now have a cone $z=\sqrt{2x^2+2y^2}$ and I think the parametric equation I normally use won't work anymore. Which would be a more suitable one in this case? Is there any generic parametric equation for cones, because one of the form $z=\sqrt{4x^2+y^2}$ would also have a different one.

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Let $z=\sqrt{a^2 x^2 + b^2 y^2}$ where $a>0$ and $b >0$
Then let $z=r$, $x=\frac{r}{a} cos(\theta)$ and $y= \frac{r}{b} sin(\theta)$