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CHAPTER 8
Three points N, Y and W are at sea level. Y is the foot of a vertical
Example 2
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
COMP/Deg mode.
-1
tan
SHIFT
5
tan
=
7
The angle of elevation of X from N is approximately 11.44°.
YW
2 . Use the formula
sin
40
2
5
7
sin
5
¡
YW is approximately 215.65m.
3 . Perform this calculation right after step 2. Using
-1
tan
SHIFT
tan
5
Hence, the angle of elevation of X from W is approximately 13.56°.
Angles of Elevation and Depression
∠XNY
tan
b
a
/
2
2
c
257
=
to find the distance YW
°
°
sin
50
sin
4
X
=
0
b
2
a
/
Ans
c
X
Y
N
52
=
. Make sure your calculator is in
257
5
tan
-1
Y
.
40°
N
0
257Xsin 40¡sin 50
52
∠
=
tan
XWY
, press
YW
=
-1
tan
W
52ª257
11.43849422
W
50°
215.6486052
52ªAns
13.5570993
22
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