Algebra II: Conic Sections Algebra II: Conic Sections | Page 10

Introduction

When looking at a cone, a circle will be created if the plane is perpendicular to the x-axis when cutting a single cone. A circle

is the set of all points in a plane that are at a fixed distance, called the radius, from a fixed point, called the center. The equation of a circle should be in the form:

Practice Graphing

Using desmos.com, type the following circle equations into the graphing calucaltor.

What do you notice when the r changes? What to you think r represents for the circle?

Practice Identifying

Now you will use a desmos manipulative to identify how h and k effect the equation the graph of the circle.

Click here the circle graph below. It will take you to the desmos site. Slide the blue bottom under h or k.

What happened when your h value increased? decreased? What happened when your k value increased? decreased? Could you move the circle diagonally?

Your Turn

Now try graphing the following equations on graph paper. Label the center and the radius for each equation. You can check

your answers usiing the desmos online graphing calculator or in the back of this book.

Circles

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