 # CIRCUMFERENCE: or If you unwrap a circle, how long will the line be?

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CIRCUMFERENCE: or If you unwrap a circle, how long will the line be?
The distance around the circle. If you unwrap a circle, how long will the line be? or So what is  anyway?

AREA FORMULA r The area of a circle with radius r is given by
This gives us the EXACT number of squares! r (It’s usually not a whole number.)

Fraction of a Circle What fraction of the whole circle is a given arc? Find the measure of the central angle. Divide by 360, the total number of degrees in the circle. 180º diameter This arc is one-half of a circle.

Fraction of a Circle 140º 220º = 220º
What fraction of the whole circle is this (major) arc? Find the measure of the central angle. The major arc measure is: 360º – minor arc measure = 360º - 140º = 220º Divide by 360, the total number of degrees in the circle. 140º 220º This arc is eleven-eighteenths of a circle.

Arc Length Formula Arc Length
= (fraction of the circle) X (circumference) = fr x C = x 2r = x 2r

Example: Find the Arc Length
A.L. (arc length) = fraction *circ. = Exact Answer (in terms of ) in in Approximate Answer (nearest tenth)

SECTOR sector of a circle - part of the interior of a circle bounded by two radii and an arc.

AREA OF A SECTOR The area of a sector of a circle The size of a slice of pizza. The FRACTION OF THE CIRCLE multiplied by the AREA OF THE CIRCLE.

Area of a Sector Formula
= (fraction of the circle) X (area of circle) = fr x A = X r2

Example: Find the Area of the Sector
A.S. (area of a sector) = fraction *area 72° Exact Answer (in terms of ) in2 Approximate Answer (nearest tenth) in2

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