AREA OF CIRCLES AND SECTORS

Area of a circle

• The area of a circle is π times the square of the radius, or A= πr2

Examples

• Find the area of a circle with radius 8 inches. A=πr2

=π*82

= π*64 = 201.06 ( approximately)Also, when we have a diameter we need only take

half of the diameter since d=1/2r.

Area of a Sector

• The ratio of the area A of a sector of a circle to the area of the circle is equal to the ratio of the measure of the intercepted arc to 360 degrees.

Examples

• Find the area of the sector such the sector cpd intercepts an arc whose measure is 80 degees. The radius is 4 ft.

**Work on your own for 2 minutes***

Using Areas of Circles and Regions

• To determine the area of a shaded region inside a circle, you will need to follow this formula:

• Area of Shaded Region=Area of a circle-Area of non-shaded region.

Homework:

• Complete the handout and bring it back before next class for credit.