What is the angle of elevation of the sun when the length of the shadow of a pole is equal to its height?

Find the angle of elevation of the sum (sun's altitude) when the length of the shadow of a vertical pole is equal to its height.

Let θ be the angle of elevation of the sun. Let AB be the vertical pole of height h and BC be the shadow of equal length h.

Here we have to find the angle of elevation of the sun.

We have the corresponding figure as follows.

What is the angle of elevation of the sun when the length of the shadow of a pole is equal to its height?

So we use trigonometric ratios to find the required angle.

In a triangle ABC

`=> tan theta = (AB/(BC)`

`=> tan theta = h/h`

`=> tan theta = 1

`=> theta = 45^@`

Hence the angle of evevation of sun is  45°

Concept: Heights and Distances

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An aeroplane at an altitude of 200 metres observes the angles of depression of opposite points on the two banks of a river to be 45° and 60°. Find the width of the river.

Let the position of the aeroplane be A, B and C be two points on the two banks of a river such that the angles of depression at B and C are 45° and 60° respectively. Let BD = x m, y m andAD = 200 m.

What is the angle of elevation of the sun when the length of the shadow of a pole is equal to its height?


In right triangle ABD, we have

What is the angle of elevation of the sun when the length of the shadow of a pole is equal to its height?


In right triangle ACD, we have

What is the angle of elevation of the sun when the length of the shadow of a pole is equal to its height?


Adding (i) and (ii), we get

What is the angle of elevation of the sun when the length of the shadow of a pole is equal to its height?


Hence, the width of the river is 315.4 metres.

If the height of a vertical pole is equal to the length of its shadow on the ground, the angle of elevation of the sun is a 0∘ b 30∘ c 45∘ d 60∘

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