Question

A 9m long ladder rests at 9m below a vertical wall. If the angle of elevation of the top of the wall from the foot of the ladderis 60°. Find the height of the wall.​
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Answer 1

Height of the wall is 27 m.

Explanation:

Let the height of the wall = h

Length of the ladder = 9 m

Angle of elevation = 60°

Ladder rests at 9 m below a vertical wall.

So, length of the wall upto which the ladder rests = h - 9

We know,

Cos Ф = base/ hypotenuse

cos 60° = length of the ladder / height of wall upto which the ladder rests

               $\frac{1}{2} = \frac{9}{h - 9}$

So,

h - 9 = 18

h = 27

Therefore, height of the wall is 27 m