1. Chapter 9 Lesson 3
Objective: To use angles of elevation and depression to solve problems.

2. Angle of Elevation
An angle of elevation is the angle formed by a horizontal line and the line of sight to an object above the horizontal line.

3. Angle of Depression
An angle of depression is the angle formed by a horizontal line and the line of sight to an object below the horizontal line.

5. Example 1: Identifying Angles of Elevation and Depression
Describe each angle as it relates to the situation shown:

6. Example 2: Real-World Connection
Surveying To find the height of Delicate Arch in Arches National Park in Utah, a surveyor levels a theodolite with the bottom of the arch. From there, she measures the angle of elevation to the top of the arch. She then measures the distance from where she stands to a point directly under the arch. Her results are shown in the diagram. What is the height of the arch?
So x ≈ 40. To find the height of the arch, add the height of the theodolite. Since = 45, Delicate Arch is about 45 feet high.

7. Example 3: Real-World Connection
Aviation To approach runway 17 of the Ponca City Municipal Airport in Oklahoma, the pilot must begin a 3° descent starting from an altitude of 2714 ft. The airport altitude is 1007 ft. How many miles from the runway is the airplane at the start of this approach?
The airplane is 2714 − 1007, or 1707 ft above the level of the airport. Use trigonometry to find the desired distance.
The airplane is about 6.2 mi from the runway at the start of the approach.

8. Assignment
Page 484
#1-17