Question

2. The angle of elevation of the top of a vertical
cliff, as seen from a boat 120 m away, is 32°.
The angle of elevation of the top of a flagpole
at the edge of the cliff, as seen from the boat,
is 37º. Find the height of the flagpole.
​

Answer 1

Answer: 15.44 m

Step-by-step explanation:

We can think this as two triangle rectangles.

In both cases, the adjacent cathetus is 120m.

When the angle is 32°, the opposite cathetus will be the height of the cliff.

When the angle is 37°, the opposite cathetus will be the heigth of the cliff plus the height of the flagpole.

Then we need to compute both of them and calculate the difference.

We can use the trigonometric relation:

Tan(θ) = (opposite cathetus)/(adjacent cathetus)

in this case we have:

Tan(32°) = (height of the cliff)/(120m)

Tan(32°)*120m = height of the cliff = 74.98m

Now we can use the other angle to compute:

Tan(37°) = (heigth of the cliff + heigth of the flagpole)/120m

Tan(37°)*120m = heigth of the cliff + heigth of the flagpole = 90.42m

Then the height of the flagpole will be:

H = 90.42m - 74.98m = 15.44 m