1. Evaluating Trigonometric Functions
Honors Algebra II Trigonometry

2. Essential Question:
How do you evaluate trigonometric functions using reference angles?
Essential Vocabulary:
Reference Angle

3. Reference Angle
A Reference Angle is the acute angle formed by the terminal side of 𝜃 and the x-axis.
Reference angles are denoted by 𝜃 ′

4. Reference Angles Cont….
If 𝜃 is an angle in Quadrants II or III:
Ask yourself: How far is it from 𝟏𝟖𝟎 ° 𝒐𝒓 𝝅?
If 𝜃 is an angle in Quadrant IV:
Ask yourself: How far is it from 𝟑𝟔𝟎 ° 𝒐𝒓 𝟐𝝅 ?
Can we find a pattern with the angles on the Unit Circle?

5. D E G R E E S 45° -- ends in a 5 Ex: 45°, 135°, 225°, 315°
30° -- divisible by 3, not divisible by 6
(ignoring the 0 at the end)
Ex: 30°, 150°, 210°, 330°
60° -- divisible by 3 and divisible by 6
Ex: 60°, 120°, 240°, 300°
D E G R E E S

6. R A D I A N S 𝜋 6 -- (30°) denominator of 6
Ex: 𝜋 6 , 5𝜋 6 , 7𝜋 6 , 11𝜋 6
𝜋 (45°) denominator of 4
Ex: 𝜋 4 , 3𝜋 4 , 5𝜋 4 , 7𝜋 4
𝜋 (60°) denominator of 3
Ex: 𝜋 3 , 2𝜋 3 , 4𝜋 3 , 5𝜋 3
R A D I A N S

7. Homework
Homework 9.6
Quiz tomorrow