circumference: the distance around the circle. if you unwrap a circle, how long will the line be?...
Post on 13-Jan-2016
216 Views
Preview:
TRANSCRIPT
CIRCUMFERENCE:The distance around the circle.
If you unwrap a circle, how long will the line be?
C d or 2C rSo what is ?anyway
AREA FORMULA
The area of a circle with radius r
is given by
2A rr
This gives us the
EXACT number of squares!
(It’s usually not a whole
number.)
Fraction of a Circle What fraction of the
whole circle is a given arc?
1. Find the measure of the central angle.
2. Divide by 360, the total number of degrees in the circle.
diameter
180º
180 1
360 2
This arc is one-half of a circle.
Fraction of a Circle What fraction of the whole
circle is this (major) arc?1. Find the measure of the
central angle. The major arc measure is:
360º – minor arc measure
= 360º - 140º= 220º
1. Divide by 360, the total number of degrees in the circle.
This arc is eleven-eighteenths of a circle.
140º
220º
220 11
360 18
Arc Length Formula
Arc Length= (fraction of the circle) X (circumference)
= fr x C
= x 2r = x 2r
central angle
360
a
360
Example: Find the Arc LengthA.L. (arc length)
= fraction *circ.
=
in
aC
36072
2 836016
510.1
in Exact Answer (in terms of )
Approximate Answer (nearest tenth)
SECTORsector 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 circleThe size of a slice of pizza. The FRACTION OF THE CIRCLE
multiplied by the AREA OF THE CIRCLE.
Area of a Sector Formula
Area of a Sector
= (fraction of the circle) X (area of circle)
= fr x A
= X r2
= X r2
central angle
360
a
360
A.S. (area of a sector)= fraction *area
72°
in2
in2
Exact Answer (in terms of )
Approximate Answer (nearest tenth)
Example: Find the Area of the Sector
2
aA
36072
836064
540.2
top related