Question

Obtain the parametric equation of the circle represented by $x^2+y^2=4$

Answer 1

Fact: Parametric equation of $(x-h{)}^2+(y-k{)}^2=r^2$ is given by

$x=h+r\cos \theta ,y=k+r\sin \theta$

In circle $h=0,k=0$ and $r=2$

Thus parametric equation of $x^2+y^2=4$ is $x=2\cos \theta$ and $y=2\sin \theta$