1. ©G Dear 2009 – Not to be sold/Free to use
Mathematics
General Preliminary
Right
Triangles
Elevation and
Depression.
Stage 6
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©G Dear 2009 – Not to be sold/Free to use

2. Elevation & Depression (1/5)Up
Elevation θ θ
Depression
Down

3. Angle of Elevation (2/5) A boat is 100 m from a lighthouse.
The height og the Lighthouse is 6 m.
What is the lighthouse’s angle of elevation? 6
100
tan θo =
θo = tan-1 (6 ÷ 100)
θo = o 6m
θo = 3.4o m θo
100m

4. Angle of Depression (3/5)
An aero plane is 1 km from a runway.
It is at a height of 300 m.
What is the planes angle of depression?
1,000m θO
300
1000
Tan θo =
300 m
θo = tan-1 (0.3)
θo = o
θo = 17o

5. Angle of Elevation (4/5) A boat is 100m from a lighthouse.
It has an angle of elevation of 30o.
What is the height of the lighthouse? (h) h
100
tan 30o =
h = 100 x Tan 30o
h = h
h = 57.7 m
30o
100m

6. Angle of Depression (5/5)
An aero plane is 3 km from a runway.
The angle of depression is 15o.
What is the altitude of the plane?
3 km
15O a 3
tan 15o = a
a = 3 x Tan 15o
a = km
a = 804 m