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Lesson 4.1 Radian & Degree Measure. Parts and Types of Angles. Terminal & Initial. Positive & Negative. Coterminal A positive and negative angle where. 30 o & ______. 120 o & ______. Investigate Draw a circle and make up a number for the radius. - PowerPoint PPT Presentation
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Lesson 4.1Radian & Degree Measure
Parts and Types of AnglesTerminal & Initial Positive & Negative
Coterminal
A positive and negative angle where
on360
30o & ______
120o & ______
Investigate1. Draw a circle and make up a number for the radius.
2. Estimate a sector where the arc length would be equal to the radius
3. Find the circumference of the circle.
4. Use the formula below to find the degree measure of the arc
5. Then, what is the measure of the central angle of your sector?
6. Write your results in the table:
oangle ncecircumfere
lengtharcmARC 360_
radius
Circ.
mARC
angle
RadianThe angle size when the arc length equals the radius of a circle
Full revolution:
2rs
rs 2
rado _2360
rado _180
rad_2
Question: How many radians to equal 180o? 360o?
Radian MeasuresThe units of an angle are in degrees or radians
orad180
deg
o
rad 180deg Units haveto cancel
Converting
Examples
Sketch in standard position.
Find 2 coterminal angles to
Arc Length and Speed
rs Arc Length =
Linear Speed =ts
Angular Speed = t
Speed = Distance over time
Units = radians
Example
Find the angle in degrees
31 in.
12 in.𝜃
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