1. Lesson 9.1 Right Triangle Trigonometry (Day 2)
Learning Goal: (G-SRT.C.8 - Pre-requisite Skill)
I can evaluate trigonometric functions of acute angles.
I can find unknown side lengths and angle measures of right triangles.
Essential Question: How can you find a trigonometric function of an acute angle θ?
Homework Discussion
5 in
5 mi
8.6 km
14.1 mi yd km m yd
9. yes
10. yes
11. no
12. no
13. yes
14. yes

2. Special Right Triangles
Know These
45°-45°-90°
30°-60°-90° 1
45° 1 2
30°
60°
sin 45° =
sin 30° = =

3. Finding an Unknown Side Length
Find the value of x for the right triangle.
Ex 1: 12
Ex 2:
60° x

4. Solving a Triangle: finding the unknown side lengths and angle measures of a triangle. Use technology.
Ex 1:
Solve △ABC. c
34°
b=13 a
Ex 2:
Solve △ABC.

5. Group Consensus
1. Find the value of x for the right triangle shown.
Solve △ABC using the diagram and 
the given measurements.
2. B = 45°, c = A = 32°, b = 10
4. A = 71°, c = B = 60°, a = 7

6. Solving Real-Life Problems
You are hiking near a canyon. While standing
at A, you measure an angle of 90º between B
and C, as shown. You then walk to B and
measure an angle of 76° between A and C.
The distance between A and B is about 2
miles. How wide is the canyon between A
and C?

7. Example:
A parasailer is attached to a boat with a rope 72 feet long. The angle of elevation from the boat to the parasailer is 28°. Estimate the parasailer’s height above the boat.

8. Practice to Strengthen Understanding
Exit Question:
What does the standard deviation tell us about a data distribution?
Practice to Strengthen Understanding
Hmwk #32 Big Ideas p466 #21-26, odd