Question

Find equation of circle whose radius is 3 and center is origin??

Answer 1

`x^2+y^2=9`

Explanation:

The general equation of a circle is:

`(x-h)^2+(y-k)^2=r^2`

We want a circle with an a center `(h,k)` centered at the origin.
Therefore `(h,k)=(0,0)`

We also want a radius `3` so `r^2=(3)^2=9`

Given these values, we can substitute into our equation to get:

`(x-0)^2+(y-0)^2=9`

Simplify and we get the equation:

`x^2+y^2=9`

This is the equation we want and its graph looks like

graph{x^2+y^2=9 [-10, 10, -5, 5]}