1. Trig Ratios C 5 2 A M 4. If C = 20º, then cos C is equal to:
Be sure to discuss if C = 20, then sin C would equal ?
4. If C = 20º, then cos C is equal to:
A. sin 70 B. cos 70 C. tan 70

2. Skills Check

3. CCGPS Geometry Day 39 (10-3-14)
UNIT QUESTION: What patterns can I find in right triangles?
Standard: MCC9-12.G.SRT.6-8
Today’s Question:
How do we use trig ratios to find the missing sides and angles of a triangle?

4. Using Trig to Find Missing Angles and Missing Sides

5. Finding a missing angle
Finding a missing angle. (Figuring out which ratio to use and an inverse trig button.)

6. Ex: 1. Figure out which ratio to use. Find x
Ex: 1 Figure out which ratio to use. Find x. Round to the nearest tenth. O
20 m
40 m A x
Shrink yourself down and stand where the angle is.
Identify the given sides as H, O, or A.
What trig ratio is this?

7. Ex: 2. Figure out which ratio to use. Find x
Ex: 2 Figure out which ratio to use. Find x. Round to the nearest tenth. O H
15 m
50 m x
Shrink yourself down and stand where the angle is.
Identify the given sides as H, O, or A.
What trig ratio is this?

8. Ex. 3: Find . Round to the nearest degree.
17.2 9 A

9. Ex. 4: Find . Round to the nearest degree.7 23 H

10. Ex. 5: Find . Round to the nearest degree.
200 O
400 H

11. Finding a missing side. (Figuring out which ratio to use and getting to use a trig button.)

12. Ex: 6. Figure out which ratio to use. Find x
Ex: 6 Figure out which ratio to use. Find x. Round to the nearest tenth.
20 m x A O

13. Ex: 7 Find the missing side. Round to the nearest tenth.
80 ft x O A

14. Ex: 8 Find the missing side. Round to the nearest tenth.

15. Ex: 9 Find the missing side. Round to the nearest tenth.
20 ft x A

16. When we are trying to find a side we use sin, cos, or tan.
When we are trying to find an angle we use (INVERSE) sin-1, cos-1, or tan-1.

17. Classwork
Missing Angles
and Sides WS