Download Geometry Fall 2011 Lesson 17 (S.A.S. Postulate)

1
Lesson Plan #83
Class: Geometry
Topic: Radian Measure
Date: Tuesday March 27th, 2012
Aim: How do we find the length of an arc?
Objectives:
1) Students will be able to find the length of an arc.
HW # 83: 𝜃 is the measure of a central angle that intercepts are arc of length s in a circle with a radius of length r.
Do Now:
PROCEDURE:
Write the Aim and Do Now
Get students working!
Take attendance
Give Back HW
Collect HW
Go over the Do Now
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In the past we have measured angles using degrees as the unit of measure. How would you describe how big is a degree?
Another unit of measure for measuring the opening of an angle is a radian.
How big is a radian?
Definition: A radian is the measure of an angle that when drawn as a central angle, would intercept an arc whose length is equal to
the length of a radius of a circle.
Let’s see how we can find out how many degrees equals one radian.
How can we find the length of an arc of a circle given the radius and degree measure in radians?
Online Activities:
http://www.mathopenref.com/radians.html
http://www.mathwarehouse.com/trigonometry/radians/convert-degee-to-radians.php
Assignment #1:
Find the radian measure of an angle of the given degree measure
A) 30o
B) 90o
C) 45o
4) 120o
D) 160o
E) 180o
F) 270o
G) 360o
Assignment #2:
Find the degree measure of an angle of the given radian measure.
𝜋
A)
3
𝜋
B)
Assignment #3:
9
𝜋
C)
10
2𝜋
D)
5
𝜋
E)
2
F)
𝜋
3𝜋
G)
4
3
http://www.mathwarehouse.com/trigonometry/radians/s=r-theta-formula-equation.php
If the angle is given in degrees, then the arc length can be found using the formula
𝑆 = 𝑟 ∙ (𝜃 ∙
http://www.mathopenref.com/arclength.html
𝜋
)
180
Assignment #4:
Find the length of an arc of a circle intercepted by a central angle with degree measure
A) 30o
B) 90o
C) 45o
4) 120o
D) 160o
E) 180o
F) 270o
G) 360o