2. Chapter 8: The Unit Circle and the Functions of Trigonometry
8.1 Angles, Arcs, and Their Measures
8.2 The Unit Circle and Its Functions
8.3 Graphs of the Sine and Cosine Functions
8.4 Graphs of the Other Circular Functions
8.5 Functions of Angles and Fundamental Identities
8.6 Evaluating Trigonometric Functions
8.7 Applications of Right Triangles
8.8 Harmonic Motion

3. 8.1 Angles, Arcs, and Their Measures
Basic Terminology
Two distinct points A and B determine the line AB.
The portion of the line including the points A and B is the line segment AB.
The portion of the line that starts at A and continues through B is called ray AB.
An angle is formed by rotating a ray, the initial side, around its endpoint, the vertex, to a terminal side.

4. 8.1 Degree Measure Degree Measure There are 360° in one rotation.
Divided the circumference of the circle into 360 parts.
There are 360° in one rotation.
An acute angle is an angle between 0° and 90°.
A right angle is an angle that is exactly 90°.
An obtuse angle is an angle that is greater than 90° but less than 180°.
A straight angle is an angle that is exactly 180°.

5. 8.1 Finding Measures of Complementary and Supplementary Angles
If the sum of two positive angles is 90°, the angles are called complementary.
If the sum of two positive angles is 180°, the angles are called supplementary.
Example Find the measure of each angle in the given figure.
(a) (b)
(Complementary angles)
(Supplementary angles)
Angles are 60 and 30 degrees
Angles are 72 and 108 degrees

6. 8.1 Calculating With Degrees, Minutes, and Seconds
One minute, written 1', is of a degree.
One second, written 1", is of a minute.
Example Perform the calculation
Solution '
Since 75' = 1° + 15', the sum is written as 84°15'.

7. 8. 1. Converting Between Decimal Degrees
8.1 Converting Between Decimal Degrees and Degrees, Minutes, and Seconds
Example
(a) Convert 74º814 to decimal degrees.
(b) Convert º to degrees, minutes, and seconds.
Analytic Solution
(a) Since

8. 8. 1. Converting Between Decimal Degrees
8.1 Converting Between Decimal Degrees and Degrees, Minutes, and Seconds
(b)
Graphing Calculator Solution

9. 8.1 Coterminal Angles Quadrantal Angles are angles in standard
position (vertex at the
origin and initial side
along the positive x-
axis) with terminal sides
along the x or y axis,
i.e. 90°, 180°, 270°, etc.
Coterminal Angles are
angles that have the same
initial side and the same
terminal side.

10. 8.1 Finding Measures of Coterminal Angles
Example Find the angles of smallest possible positive
measure coterminal with each angle.
(a) 908° (b) –75°
Solution Add or subtract 360° as many times as
needed to get an angle between 0° and 360°.
(a)
(b)
Let n be an integer, we have an infinite number of
coterminal angles: e.g. 60° + n· 360°.

11. 8.1 Radian Measure An angle with its vertex at the
The radian is a real number, where the degree is a unit of measurement.
The circumference of a circle, given by C = 2 r, where r is the radius of the circle, shows that an angle of 360º has measure 2 radians.
An angle with its vertex at the
center of a circle that intercepts
an arc on the circle equal in
length to the radius of the circle
has a measure of 1 radian.

12. 8.1 Converting Between Degrees and Radians
1. Multiply a degree measure by  /180º radian and simplify to convert to radians.
2. Multiply a radian measure by 180º/ and simplify to convert to degrees.

13. 8.1 Converting Between Degrees and Radians
Multiply a degree measure by  /180º and simplify to convert to radians. For example,
Multiply a radian measure by 180º/ and simplify to convert to degrees. For example,

14. 8. 1. Converting Between Degrees and
8.1 Converting Between Degrees and Radians With the Graphing Calculator
Example Convert 249.8º to radians.
Solution
Put the calculator in radian mode.
Example Convert 4.25 radians to degrees.
Put the calculator in degree mode.

15. 8.1 Equivalent Angle Measures in Degrees and Radians
Figure 18 pg 9

16. 8.1 Arc Length
The length s of the arc intercepted on a circle of radius r by a central angle of measure  radians is given by the product of the radius and the radian measure of the angle, or
s = r,  in radians.

17. 8.1 Arc Length Example A circle has a radius of 18.20 centimeters.
Find the length of an arc intercepted by a central angle of 144º.
Solution

18. 8.1 Area of a Sector
The area of a sector of a circle of radius r and central angle is given by

19. 8.1 Linear and Angular Speed
Angular speed  (omega) measures the speed of rotation and is defined by
Linear speed  is defined by
Since the distance traveled along a circle is given by the arc length s, we can rewrite  as

20. 8.1 Finding Linear Speed and Distance Traveled by a Satellite
Example A satellite traveling in a circular orbit 1600 km
above the surface of the Earth takes two hours to complete an
orbit. The radius of the Earth is 6400 km.
Find the linear speed of the satellite.
Find the distance traveled in 4.5 hours.
Figure 24 pg 12

21. 8.1 Finding Linear Speed and Distance Traveled by a Satellite
Solution
(a) The distance from the Earth’s center is
r = = 8000 km.
For one orbit,  = 2, so s = r = 8000(2) km. With
t = 2 hours, we have
(b) s =  t = 8000 (4.5)  110,000 km