Mr. SaucedoMilby High School

Geometry

Objective:To find partial areas and circumferences of circles.

What you should know…Find the

Circumference and the Area of a circle with diameter 10.

WHAT IS?ARC LENGTH

An arc length is a fraction of the circumference.

The concept…Can you find the arc length of thisSemicircle?

What would the arc length be if we just wanted to use a quarter of the circle?

HOW DO WE FIND ARC LENGHTS?

With the following proportion:

Part of a circumference = Portion of degrees

Whole Circumference Whole: Degrees in a circle

Arc length = Central Angle пD 360

GUIDED EXAMPLE 1Find the length of the arc:

Independent exampleFind the length of the arc AB.

SECTORSWhat is a sector?

AREA OF A SECTORFORMULA:

AREA OF SECTOR = CENTRAL ANGLEAREA OF CIRCLE 360

AREA OF SECTOR = CENTRAL ANGLE пr2 360

GUIDED EXAMPLE 2Find the area of the blue section

INDEPENDENT EXAMPLEFind the area of the shaded region.

HOMEWORKWORKBOOK (BLUE BOOK)

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