Reference angle in Trigonometry

1. GOOD
AFTERNOON
EVERYONE 

3. Reference Angle- Let 𝜃 be a non-quadrantal angle
in standard position. The reference angle of 𝜃 is
the acute angle 𝜃𝑅 that the terminal side of 𝜃
makes with the x-axis.

4. Finding the Reference Angle

5. Finding the Reference Angle

6. •Example 1: Find the reference angle for
each of the following angles
1. 120°
2.
−15𝜋
4
3. -30°

7. •Example 2: Use preference angle and
appropriate sign to find the exact value
of each expression.
1. sin(
11𝜋
6
) and cos(
11𝜋
6
)
2. cos(−
7𝜋
6
)
3.sin 150 °

8. •More solved problems:
1. If P(𝜃) is a point on the unit circle and 𝜃 =
17𝜋
3
, what are the coordinates of P(𝜃)?
2. If
3𝜋
2
< 𝜃 < 2𝜋, find 𝜃 if cos 𝜃 = sin
2𝜋
3
.