1. Introduction to Trigonometry
Angles and Radians
(MA3A2): Define an understand angles measured in degrees and radians.

2. Lowercase Greek letters are used to denote angles
Θ (theta)
α (alpha)
β (beta)
γ (gamma)

3. Reference Angle: the acute angle formed by the terminal side and the closest x-axis.
QUADRANT I
QUADRANT II
QUADRANT III
QUADRANT IV

4. EXS: Find the reference angle for the following angles of rotation.
10. Θ = 405°
11. Θ = 210 °
12. Θ = -300 °
13. Θ = -225 °

5. ON YOUR OWN: Find the reference angle for the following angles of rotation.
10. Θ = 405°
11. Θ = 210 °
45°
3𝟎°
12. Θ = -300 °
13. Θ = -225 °
6𝟎°
45°

6. **Reference angles are ALWAYS positive!!
Reference Angle: the acute angle formed by the terminal side and the closest x-axis.
**Reference angles are ALWAYS positive!!
EX: Find the reference angle for each angle.
Θ = 115°.
65°

7. **Reference angles are ALWAYS positive!!
Reference Angle: the acute angle formed by the terminal side and the closest x-axis.
**Reference angles are ALWAYS positive!!
EX: Θ = 225°.
45°

8. **Reference angles are ALWAYS positive!!
Reference Angle: the acute angle formed by the terminal side and the closest x-axis.
**Reference angles are ALWAYS positive!!
EX: Θ = 330°
3𝟎°

9. **Reference angles are ALWAYS positive!!
Reference Angle: the acute angle formed by the terminal side and the closest x-axis.
**Reference angles are ALWAYS positive!!
EX: Θ = -150°.
3𝟎°

10. **If Θ lies in the first quadrant, then the angle is it’s own reference angle.
EX: Θ = 60°.
6𝟎°