1. Angles and their Measures
Lesson 1

2. As derived from the Greek Language, the word trigonometry means “measurement of triangles.”
Initially, trigonometry dealt with relationships among the sides and angles of triangles and was used in the development of astronomy, navigation, and surveying.

3. With the development of Calculus and the physical sciences in the 17th Century, a different perspective arose – one that viewed the classic trigonometric relationships as functions with the set of real numbers as their domain.
Consequently the applications expanded to include physical phenomena involving rotations and vibrations, including sound waves, light rays, planetary orbits, vibrating strings, pendulums, and orbits of atomic particles.

4. We will explore both perspectives beginning with angles and their measures…..
An angle is determined by rotating a ray about its endpoint.
The starting position of called the initial side. The ending position is called the terminal side.

5. Standard Position Vertex is at the origin, and the initial side is on the x-axis.
Terminal Side
Initial Side

6. Positive Angles are generated by counterclockwise rotation.
Negative Angles are generated by clockwise rotation.
Let’s take a look at how negative angles are labeled on the coordinate graph.

7. Negative Angles Go in a Clockwise rotation

9. Coterminal Angles
Angles that have the same initial and terminal side. See the examples below.

10. Coterminal Angles They have the same initial and terminal sides.
Determine 2 coterminal angles, one
positive and one negative for a 60
degree angle.
= 420 degrees
60 – 360 = -300 degrees

11. Give 2 coterminal angles.
= 390 degrees
30 – 360 = -330 degrees

12. Give a coterminal angle, one positive and one negative.
= 590 degrees
230 – 360 = -130 degrees

13. Give a coterminal angle, one positive and one negative.
= 340 degrees
-20 – 360 = -380 degrees

14. Give a coterminal angle, one positive and one negative.
Good but
not best
answer.
= 820 degrees
460 – 360 = 100 degrees
100 – 360 = -260 degrees

15. Complementary Angles Sum of the angles is 90
Find the complement of each angles:
40 + x = 90
x = 50 degrees
No Complement!

16. Supplementary Angles Sum of the angles is 180
Find the supplement of each angles:
40 + x = 180
x = 140 degrees
120 + x = 180
x = 60 degrees

17. Coterminal Angles: To find a Complementary Angle: To find a Supplementary Angle:

18. Radian Measure
One radian is the measure of the central angle, , that intercepts an arc, s, that is equal in length to the radius r of the circle.
So…1 revolution is equal to 2π radians

19. Let’s take a
look at them
placed on the
unit circle.

20. Radians
Now, let’s add more…..

21. Radians

22. More Common Angles
Let’s take a look at more common angles that are found in the unit circle.

23. Radians

24. Radians

25. Look at the Quadrants

26. Determine the Quadrant of the terminal side of each given angle.
Go a little more than one quadrant – negative. Q3
A little more than one revolution. Q1

27. Determine the Quadrant of the terminal side of each given angle.Q3 Q2
2 Rev degrees. Q4

28. Coterminal Angles using Radians

29. Find a coterminal angle.
There are an infinite number of coterminal angles!

30. Give a coterminal angle, one positive and one negative.

31. Give a coterminal angle, one positive and one negative.

32. Find the complement of each angles:

33. Find the supplement of each angles:

34. Find the complement & supplement of each angles, if possible:
None

35. Coterminal Angles: To find a Complementary Angle: To find a Supplementary Angle:
RECAP

36. Conversions

37. NOTE: The answer is in radians!

40. Convert 2 radians to degrees

41. Arc Length Arc Length = (radius) (angle)
The relationship between arc length, radius, and central angle is
Arc Length = (radius) (angle)

42. 1st Change 240 degrees into radians.