Geometry HIgh School, lesson, Circles, Areas, Arc Lengths, Sectors, Introduction, Perimeter, Area, Volume Unit

1. Mr. Saucedo
Milby High School
Geometry

2. Objective:
To find partial areas and
circumferences of circles.

3. What you should know…
Find the
Circumference and the
Area of a circle with
diameter 10.

4. WHAT IS?
ARC LENGTH
An arc length is a fraction of the circumference.

5. The concept…
Can you find the arc length of this
Semicircle?
What would the arc length be if we just wanted to use a
quarter of the circle?

6. HOW DO WE FIND ARC LENGHTS?
With the following proportion:
Part of a circumference
Whole Circumference
circle
Arc length
пD
=
Portion of degrees
Whole: Degrees in a
= Central Angle
360

7. GUIDED EXAMPLE 1
Find the length of the arc:

8. Independent example
Find the length of the arc AB.

9. SECTORS
What is a sector?

10. AREA OF A SECTOR
FORMULA:
AREA OF SECTOR
AREA OF CIRCLE
=
CENTRAL ANGLE
360
AREA OF SECTOR = CENTRAL ANGLE
пr2
360

11. GUIDED EXAMPLE 2
Find the area of the blue section

12. INDEPENDENT EXAMPLE
Find the area of the shaded region.

13. HOMEWORK
WORKBOOK (BLUE BOOK)
Pages: