5-7 Circles: Circumference and Arc Length
Transcript of 5-7 Circles: Circumference and Arc Length
5-7 Circles:
Circumference and Arc Length
Objective: Find the circumference of a circle and the length of an arc.
pi (π) = ratio of circumference of a circle to its diameter
π 3.14 22/7
Circumference (Perimeter)Theorem 5-10
The circumference of a circle is π times the diameter.
Example:
Find the circumference of a circle with a diameter of 16 cm.
concentric circles: two circles that lie in the same plane and have the same center
Example: The radii of two concentric circles is 2:1, what is the ratio of their circumferences?
Arc length: the distance along an arc measured in linear units ( ft, m, yds, etc.)
** The length of an arc is a fraction of the circumference of the circle.
Example: An arc of 90° represents 90/360 or 1/4 of the circle, so its arc length is 1/4 the circumference of the circle.
THEOREM 511
Example:Find the arc length. Give answers in terms of π and rounded to the
nearest hundredth.
120°
You Try:Find the arc length. Give your
answer in terms of π and rounded to the nearest hundredth.
Congruent arcs:arcs that have the same measure and are in the same circle or in congruent circles
Arc Length # 1Find the lengths to the nearest tenth
AND in terms of π.
HW # 55: p. 282-283# 9-13, 19-22