1. Section T1- Angles and Their Measure
MAT 204 SP09
Section T1- Angles and Their Measure
In this section, we will study the following topics:
Terminology used to describe angles
Degree measure of an angle
Radian measure of an angle
Converting between radian and degree measure

2. Angles Trigonometry translated: _____________ of _____________
Angle Measure

3. Standard Position Vertex at origin
The initial side of an angle in standard position is always located on the positive x-axis.

4. 120° –210° Angle describes the amount and direction of rotation
Positive Angle- rotates counter-clockwise (CCW)
Negative Angle- rotates clockwise (CW)

5. Positive and negative angles
When sketching angles, always use an arrow to show direction.

6. Sketching Angles (Degrees)
1. Sketch in standard position. In which quadrant is  located?
2. Sketch in standard position. In which quadrant is  located?

7. Coterminal Angles
Coterminal Angles-Two angles with the same initial and terminal sides
(Hint: +360 and -360!!)
Find 2 coterminal angles that correspond to the given angle.
Ex1) 55 º Ex2) -112 º
Ex3) 570 º Ex4) -420 º

8. We’ll start with degrees, denoted by the symbol º.
Measuring Angles
The measure of an angle is determined by the amount of rotation from the initial side to the terminal side.
There are two common ways to measure angles, in degrees and in radians. ******************************************************************
We’ll start with degrees, denoted by the symbol º.
One degree (1º) is equivalent to a rotation of of one revolution.

9. Acute and Obtuse Angles
Acute angles have measure between _____º and _____º.
Obtuse angles have measure between ____º and _____º.
Straight angles measure _______º.

10. Classifying Angles Example: 50º is a ____ quadrant angle.
Angles are often classified according to the QUADRANT in which their terminal sides lie.
Example:
50º is a ____ quadrant angle.
208º is a ____ quadrant angle II I
-75º is a _____ quadrant angle III IV

11. Classifying Angles
Standard position angles that have their terminal side on one of the axes are called QUADRANTAL ANGLES.
For example, 0º, 90º, 180º, 270º, 360º, … are quadrantal angles.

12. Complementary and Supplementary Angles
Complementary Angles
Def=Two positive angles whose sum is ______º
Angles that measure 22º and ____º are complements.
Supplementary Angles
Def=Two positive angles whose sum is _______º
Angles that measure 137º and ____º are supplements.
EX) State the complement and supplement to each given angle.
Ex1) Ex2)

13. Radian Measure Definition of Radian:
A second way to measure angles is in radians.
Definition of Radian:
One radian is the measure of a central angle  that intercepts arc s equal in length to the radius r of the circle.
In general, for  in radians,

14. MAT 204 SP09
Radian Measure

15. Radian Measure

16. ***We are going to set up a conversion chart!!!
Conversions Between Degrees and Radians
To convert degrees to radians, multiply degrees by
To convert radians to degrees, multiply radians by
***We are going to set up a conversion chart!!!
Example
Convert from Degrees to Radians: 210º

17. Conversions Between Degrees and Radians
Example
a) Convert from radians to degrees:
b) Convert from radians to degrees:

18. Conversions Between Degrees and Radians
Try it!
c) Convert from degrees to radians (exact):
d) Convert from radians to degrees:

19. Conversions Between Degrees and Radians
Again!
e) Convert from degrees to radians (leave π in your answer!):
f) Convert from radians to degrees (to nearest tenth):

20. A Sense of Angle Sizes
See if you can guess the size of these angles first in degrees and then in radians.
You will be working so much with these angles, you should know them in both degrees and radians.

21. Sketching Angles (Radians)
MAT 204 SP09
Sketching Angles (Radians)
Sketch in standard position. In which quadrant is  located?
Sketch in standard position. In which quadrant is  located?

22. Angles and Their Measure WS
MAT 204 SP09
End of Section T.1
HW:
Angles and Their Measure WS