1. Warm Up – 3/9 - Monday
Convert the following to Radians. Leave 𝜋 in your
Answer.
1. 45° 2. −135° °
Convert the following to Degrees.
4. 3𝜋 𝜋 6. − 𝜋 3

2. Coterminal Angles
Angles that land on the same spot with respect to the positive x-axis.
Differences of 360° or 2𝜋 radians

3. Reference Angles
A reference angle is the angle between any angle and the x-axis.

4. Example #1
State the reference angle.

5. Example #1 - Solution The reference angle is 180° - 150° = 30°.
30° is the measure between our terminal ray and the x-axis.
30°

6. Example #2
State the reference angle.

7. Example #2 - Solution
We know the whole angle is 25𝜋 18 while half a revolution is 𝜋.
Thus our reference angle is 25𝜋 18 −𝜋
Changing 𝜋 to a fraction over 18:
25𝜋 18 − 18𝜋 18 = 7𝜋 18

8. Coterminal and Reference Angle Classwork