Question

Find the director circle of the ellipse, $\frac{x^2}{16}+\frac{y^2}{9}=1$

Answer 1

As we know that

Director circle of the ellipse $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ is $x^2+y^2=a^2+b^2$

So the director circle of $\frac{x^2}{16}+\frac{y^2}{9}=1$ is $x^2+y^2=16+9⟹x^2+y^2=25$