# Circles

- Author:
- David

- Topic:
- Circle

## Introduction

The standard equation of a circle is given by:
This should remind you of the pythagorean theorem:

## Descriptions

Note that when a circle equation contains a negative, h and k are actually positive values.
for the circle , the center of the circle would be (h,k)=(5,-2), with a radius of 4, since
Now use the geogebra applet to see how manipulating the center and radius of a circle changes the equation of a circle in real time.