# calcul – Vertical tangent folium of Descartes

So, for the folium of descartes, there is a horizontal and vertical tagnet at $$(0,0)$$.

Using a parametric equation, $$x = 3t / (1 + t ^ 3)$$ and $$y = 3t ^ 2 / (1 + t ^ 3)$$.

Asymptotic horizontal I understand. But vertical asymptote?

There is a vertical asymptote, when $$dx / dt = 0$$but $$dx / dt$$ is equal to $$0$$ only when $$t = (1/2) ^. 333$$. This gives another point where a vertical asymptote is present.

So, how can I calculate that there is a vertical asymptote at (0,0) using these parametric equations?