Just need a tiny bit of help with Parametric/Cartesian equations involving trig (1 Viewer)

[ConHeo]

Eliminate 't' from each of the following pairs of parametric equations and so form the corresponding Cartesian equation. Make a rough sketch of each curve.

x=3cost
y=3sint

I can make a rough sketch of the curve myself, but how do I get to the corresponding Cartesian equation?
Regards

 

[HeroicPandas]

Use the fact that (sinx)^2 + (cosx)^2 = 1

 

[Praer]

Easy.

x = 3cos(t) --> x^2 = 9cos^2(t)
y = 3sint(t) --> y^2= 9sin^2(t)

Therefore add them together and you end up with

x^2 + y^2 = 9(cos^2(t)+sin^2(t))
since cos^2(t)+sin^2(t) = 1

The final Cartesian equation is x^2 + y^2 = 9, which is a circle.