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