Page 51 - DMTH201_Basic Mathematics-1

Basic Mathematics – I

Notes 8. Use calculator to approximate h.
h = (approximately) 115 meters.
The angle of elevation of an aeroplane is 23°. If the aeroplane’s altitude is 2500 m, how far away
is it?

Answer: A represents aeroplane
Let the distance be x. Then .

You can walk across the Bridge and take a photo of the House from about the same height as top
of the highest sail. This photo was taken from a point about 500 m horizontally from the House
and we observe the waterline below the highest sail as having an angle of depression of 8°. How
high above sea level is the highest sail of the House?

This is a simple tan ratio problem.
tan 8° = h/500
So
h = 500 tan 8° = 70.27 m.
So the height of the tallest point is around 70 m.

[The actual height is 67.4 m.]

2.7 Summary

(i) In this unit you have studied about trigonometric functions. There are six trigonometric
functions, these are sine, cosine, tan, cot, sec and cosec.
(ii) By Pythagorean Theorem.

2
2
sin a + cos a = 1

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