# How do you graph x^2 + y^2 = 16 and r = 4?

Apr 11, 2018

They're the same curve. Recall that $r = \sqrt{{x}^{2} + {y}^{2}}$.

$\sqrt{{x}^{2} + {y}^{2}} = 4$

${x}^{2} + {y}^{2} = 4$

Which is same as the other equation. This makes a circle with radius $2$ and centre $\left(0 , 0\right)$. Here is its graph:

graph{x^2 + y^2 = 4 [-10, 10, -5, 5]}

Hopefully this helps!