What is the equation of a circle centered at the origin with radius 13

x² + y² = 13²

Step-by-step explanation:

The standard equation of a circle with center at (h, k) and radius r is

(x - h) ² + (y - k) ² = r²

Here, (h, k) is (0, 0) and r = 13.

We thus have the following result:

x² + y² = 13²