Question

What is the radius of the circle given by the equation x^2+y^2=1 ?

A. 1
B. 2
C. 4
D. 8

Answer 1

The radius of the circle is 1, since this equation is in the form x² + y² = r², where r is the radius. So, to find the radius we know that r² = 1 --> r = 1 or r = -1. Since a radius can't be negative, we take r = 1 to be the radius of this circle.