1. 1

2. Trigonometric Ratios of an Obtuse Angle
Definition: An angle is in standard position if
• its first side (initial side) is a ray from the origin along the
positive x­axis
• its second side (terminal side) is any ray from the origin
• the angle is measured from the initial to the terminal side in a
counterclockwise direction
]
Angle is in standard position.
2

3. 3

4. 4

5. 5

6. Use the coordinate definition of the trigonometric ratios
to find sin , cos and tan if angle is in standard position
• P(3, 4) is on • P(-3, 4) is on
its terminal arm its terminal arm
6

7. Θ sinΘ cosΘ tanΘ
0
30
0
150
0
65
0
115
0
89
0
91
7

8. • Find the size of each angle (nearest tenth)
• State acute and obtuse angles where possible
1) sin = 0.42
2) cos = ­0.3
3) tan = 1.5
8

9. Assignment:
Exercise 18
9