Rewrite in rectangular form: r=5

x ^2 + y^ 2 = 25

Step-by-step explanation:

Square both sides:

r ^2 = 5^ 2

Substitute x ^2 + y^ 2 for r ^2:

x ^2 + y ^2 = 5 ^2

Insert the center - 0 into the x and y terms:

(x - 0) ^ 2 + (y - 0) ^2 = 5 ^2

This is the standard form for a circle whose center is (0, 0) and the radius is 5.