Chapter 10

Section 2

Area of a Circle

The area of a circle is the product of pi and its radius squared.


A=pi*r^2

Vocab

Area-the amount of surface the figure covers

Circle-set of all points in a plane that are the same distance from the same point called the center

Radius-distance from the center to any point on the circle

Circumference-the distance around a circle

Diameter-distance across the circle through the center, or twice the radius

Pi-the quotient of a circles diameter and circumference 3.14159...... which this constant is represented by the Greek letter pi

Example

Find the area of a circle with a radius of 2in


Step One: Write the Area formula

Step two: Substitute 3.14 for pi and substitute 2 for radius.

Step three: Multiply


A=pi*r^2

A=3.14*2^2



Answer=12.56

Real World Example

If you had a circular drive way and needed to fill in the center with grass, you would need to find the area of the circle in order to know how many rolls of grass to buy.
How to Find the Area of a Circle, Given a Radius or a Diameter