1. Let’s Get It Started . . .
30°
60° A B C
What is the correct term for side AB, opposite right C?
What is the side opposite B?
What is the leg side adjacent to B?
What is the side opposite A?
What is the leg side adjacent to A?
hypotenuse AC BC

2. Introduction to Trigonometry
Section 9.1
Introduction to Trigonometry
At the end of this lesson you will understand/apply:
sine (sin)
cosine (cos)
tangent (tan)

3. Three Trigonometric Ratios
Only for RIGHT triangles!!!!!

4. SOHCAHTOA or SohCahToaB 5 3 C A 4

5. Why? To solve triangles other than 30°-60°-90° or 45°-45°-90°.
Look on page 424 in your textbook at the Table of Trigonometric Ratios.
You have the luxury of using a calculator!
IMPORTANT: Your calculator must be in DEGREE mode.

6. Communicating 1. What happens to sin A as A increases?
The sin A increases.
2. As A increases, what number is sin A approaching? 1
Or, the sin A approaches 1 as the measure of A approaches 90.
3. Can you state/write a generalization similar to above that describes the relationship between the cos A and the measure of A.
The cos A approaches 1 as the measure of A approaches 0.

7. New Vocabulary A
Angle of elevation: The angle between an upward line of sight and the horizontal. P
of elevation H P H
Angle of depression: The angle between a downward line of sight and the horizontal.
of depression B
IMPORTANT: These angles are between a line of sight and the horizontal. Do NOT use the vertical!

8. Using Trigonometric Ratios to Find a Missing Side40
Find missing side to nearest whole number. x
27

9. Using Trigonometric Ratios to Find a Missing Side (cont.)
Find missing side to nearest whole number. x
32 70

10. Using Trigonometric Ratios to Find a Missing Side (cont.)
60 x
Find missing sides to nearest hundredth. y 4

11. Using Trigonometric Ratios to Find a Missing Angle
Find missing angles to nearest hundredth. b 7 a 24

12. Using Trigonometric Ratios to Find a Missing Angle (cont.)
Find missing angles to nearest tenth. b 9 a 12

13. Using Trigonometric Ratios to Solve a Word Problem
A boat is pulling a parasailer. The line to the parasail is 800 feet long. The angle between the line and the water is about 25. (a) How high is the parasailer? (b) How far back is the parasailer from the boat?
800
25