CHAPTER 8
Angles of Elevation and Depression
22
2
=
5
7
SHIFT
tan
-1
tan
5
2
a
b
/
c
=
2
4
0
X
¡
sin
sin
7
5
5
0
=
SHIFT
tan
-1
tan
5
2
a
b
/
c
Ans
Three points
N
,
Y
and
W
are at sea level.
Y
is the foot of a vertical
lighthouse.
N
is 257m due north of
Y
and
W
is due west of
Y
. The height
of the light house is 52m.
(a) Calculate the angle of elevation of
X
from
N
.
(b) The bearing of
W
from
N
is 040°. Calculate the distance
YW
.
(c) Calculate the angle of elevation of
X
from
W
.
OPERATION
1
. Find the angle of elevation by using
257
52
tan
=
∠
XNY
. Make sure your calculator is in
COMP/Deg
mode.
The angle of elevation of
X
from
N
is approximately 11.44°.
2
. Use the formula
°
=
°
50
sin
257
40
sin
YW
to find the distance
YW
.
YW
is approximately 215.65m.
3
. Perform this calculation right after step 2. Using
YW
XWY
52
tan
=
∠
, press
Hence, the angle of elevation of
X
from
W
is approximately 13.56°.
Example 2
tan
-1
52
ª
257
11.43849422
Y
X
W
N
257Xsin 40
¡
sin 50
215.6486052
N
Y
W
40°
50°
tan
-1
52
ª
Ans
13.5570993