1. Warm up Find the missing side.

2. Review Homework

3. Skills Check

4. CCGPS Geometry Day 18 (9-25-13)
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 solve real world problems?

5. Sin-Cosine Cofunction

6. The Sin-Cosine Cofunction

7. 1. What is sin A?
2. What is Cos C?

8. 3. What is Sin Z?
4. What is Cos X?

9. 5. Sin 28 = ?

10. 6. Cos 10 = ?

11. 7. ABC where B = 90. Cos A = 3/5 What is Sin B?

12. 8. Sin  = Cos 15 What is ?

13. Right Triangle Trigonometry
CCGPS Geometry
Applications of
Right Triangle Trigonometry

14. Solving Word Problems
Use the 3 ratios – sin, cos and tan to solve application problems.
Choose the easiest ratio(s) to use based on what information you are given in the problem.

15. Draw a Picture
When solving math problems, it can be very helpful to draw a picture of the situation if none is given.
Here is an example.
Find the missing sides and angles for Triangle FRY. Given that angle Y is the right angle, YR = 68, and FR = 88. 68 88 r
The picture helps to visualize what we know and what we want to find!

16. 1. From a point 80m from the base of a tower, the angle of elevation is 28˚. How tall is the tower?x
28˚ 80
Using the 28˚ angle as a reference, we know opposite and adjacent sides.
Use
tan
tan 28˚ =
80 (tan 28˚) = x
80 (.5317) = x
x ≈ 42.5
About 43 m

17. 2. A ladder that is 20 ft is leaning against the side of a building
2. A ladder that is 20 ft is leaning against the side of a building. If the angle formed between the ladder and ground is 75˚, how far is the bottom of the ladder from the base of the building? 20
building
ladder
75˚ x
Using the 75˚ angle as a reference, we know hypotenuse and adjacent side.
Use
cos
cos 75˚ =
20 (cos 75˚) = x
20 (.2588) = x
x ≈ 5.2
About 5 ft.

18. 3. When the sun is 62˚ above the horizon, a building casts a shadow 18m long. How tall is the building? x
62˚ 18
shadow
Using the 62˚ angle as a reference, we know opposite and adjacent side.
Use
tan
tan 62˚ =
18 (tan 62˚) = x
18 (1.8807) = x
x ≈ 33.9
About 34 m

19. 4. A kite is flying at an angle of elevation of about 55˚
4. A kite is flying at an angle of elevation of about 55˚. Ignoring the sag in the string, find the height of the kite if 85m of string have been let out.
kite 85 x
string
55˚
Using the 55˚ angle as a reference, we know hypotenuse and opposite side.
Use
sin
sin 55˚ =
85 (sin 55˚) = x
85 (.8192) = x
x ≈ 69.6
About 70 m

20. 5. A 5.50 foot person standing 10 feet from a street light casts a 14 foot shadow. What is the height of the streetlight?
5.5 x˚ 10 14
shadow
tan x˚ =
x° ≈ °
About 9.4 ft.

21. Depression and Elevation
If a person on the ground looks up to the top of a building, the angle formed between the line of sight and the horizontal is called the angle of elevation.
If a person standing on the top of a building looks down at a car on the ground, the angle formed between the line of sight and the horizontal is called the angle of depression.
horizontal
angle of depression
line of sight
angle of elevation
horizontal

22. 6. The angle of depression from the top of a tower to a boulder on the ground is 38º. If the tower is 25m high, how far from the base of the tower is the boulder?
38º
angle of depression 25
Alternate Interior Angles are congruent
38º x
Using the 38˚ angle as a reference, we know opposite and adjacent side.
Use
tan
tan 38˚ = 25/x
(.7813) = 25/x
X = 25/.7813
x ≈ 32.0
About 32 m