Lesson 2, Topic 3
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# Measuring Angle of Elevation and Depression

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#### Topic Content:

• Measuring Angle of Elevation and Depression

Theodolite: Used by surveyors

Clinometer: Made up of a protractor, a tube, and a plumbline attached to the centre of the protractor to indicate the angle.

### Example 2.3.1:

From a point, A on a level ground 27.5 cm away from the foot of a tower, the angle of elevation of the top of the tower is observed to be 44Â°.

(a) Find by scale drawing, the height of the tower.
(b) How far is point A from the height of the tower?

Solution

Step 1: Start by drawing a rough sketch

Step 2:   Choose a suitable scale. In this case, 1 cm represents 5 cm.

|AC| = 27.5 cm,

Scale = $$\frac{1 \: cm}{5\: cm}$$

27.5 cm becomes

â‡’ $$\scriptsize 27.5 \: \times \: \normalsize \frac{1 \: cm}{5 \: cm}$$

= $$\scriptsize 5.5 \: cm$$

Step 3:  Draw a horizontal line of length 5.5 cm and draw the triangle using a protractor, using a 44Â° angle.

Draw a horizontal line of 5.5 cm

Mark a 44Â° angle using a protractor

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