Transcript Lesson 7.7

7-7 Areas of Circles
and Sectors
Area of a Circle (Thm. 7-15): The
area of a circle is the product of pi
and the square of its radius.
Ex 1: How much more pizza is in a 12-in
diameter pizza than in a 10-in pizza
Sector of a Circle: a
region bounded by an
arc of the circle and the
two radii to the arc’s
endpoints.
Area of a Sector of a Circle (Thm. 7-16):
The area of a sector of a circle is the
product of the ratio and the area of the
circle.
measure of arc
2
Area of Sector 
 r
360
• A circle has a diameter of 20 cm. What
is the area of a sector bounded by a
208 major arc? Round your answer.
Segment of a Circle
Segment: a part of a circle bounded by an
arc and the segment joining its endpoints.
To find the area of a
segment for a minor arc,
draw radii to form a sector.
The area of the segment
equals the area of the
sector minus the area of
the triangle formed.