CHAPTER 8
Angles of Elevation and Depression
21
–
Ans
¡
6
0
6
2
5
tan
0
=
tan
0
4
=
=
X
An observer stands at
A
, which is at the top of a tower,
AC
. He sees a
car on the road at
B
, which is 60m from
C
. The angle of depression of
B
from
A
is
°
25 . Calculate the height of the tower.
A traffic light is located at
D
, where
CDB
is a straight
line. The angle of elevation of
A
from
D
is
°
40 .
Calculate the distance
BD
.
OPERATION
1
. Calculate the height of the tower using
°
=
25
tan
60
AC
.
The height of the tower is approximately 27.98m.
2
. To find the distance
BD
, first determine
CD
using
CD
AC
=
°
40
tan
.
Therefore,
CD
is approximately 33.34m.
3
. The distance of
CD
BC
BD
−
=
.
Hence, the distance
BD
is approximately 26.66m.
Example 1
60Xtan 25
27.97845949
Ans
¡
tan 40
33.34342961
60
–
Ans
26.65657039
60m
A
C
D
25°
B