What is the height of the cliff in this scenario?

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Discussion Overview

The discussion revolves around a geometry problem involving a tower on a cliff and the angles of depression to a point on the opposite shore of a river. Participants are attempting to determine the height of the cliff based on given angles and the height of the tower. The scope includes mathematical reasoning and problem-solving strategies.

Discussion Character

  • Mathematical reasoning
  • Homework-related
  • Exploratory

Main Points Raised

  • One participant presents the problem, asking for help to find the height of the cliff based on the angles of depression.
  • Several participants emphasize the importance of drawing a diagram to visualize the problem and identify relevant triangles.
  • A diagram is provided by one participant, prompting further calculations of angles related to the triangles formed.
  • Another participant suggests a calculation method using the law of sines, leading to a proposed height of the cliff at approximately 206.4 feet.
  • One participant questions whether a previously stated height of 190.71 feet is correct.

Areas of Agreement / Disagreement

There is no consensus on the height of the cliff, as different calculations have been proposed, and participants have not agreed on a definitive answer.

Contextual Notes

Participants have not fully resolved the mathematical steps involved in their calculations, and there may be dependencies on the accuracy of the angles and assumptions made about the geometry of the situation.

ramz
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A tower 125 feet high is on a cliff on the bank of a river. From the top of the tower, the angle of depression of a point on the opposite shore is 28.7 degrees. From the base of the tower, the angle of depression of the same point is 18.3 degrees. Find the height of the cliff. (Assume the cliff is perpendicular to the river.)

Please help me to solve this problem.
 
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Have you at least drawn a diagram? Identified a triangle? Filled in all the information you can about that triangle?
 
Prove It said:
Have you at least drawn a diagram? Identified a triangle? Filled in all the information you can about that triangle?

That's my problem too, to interpret the problem and make an illustration.

- - - Updated - - -

Please help me to interpret the problem and make an illustration or diagram because the diagram is not given. Thanks
 
Here is a diagram:

View attachment 4818

Can you begin by finding the values of the angles labeled $a,\,b,\,c,\,d$?
 

Attachments

  • cliffheight.png
    cliffheight.png
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Thanks.
 
The height of the cliff is 190.71 ft., am i right?
 
Well, we know:

$$a=90^{\circ}-28.7^{\circ}=61.3^{\circ}$$

$$a=90^{\circ}-18.3^{\circ}=71.7^{\circ}$$

$$c=18.3^{\circ}$$

$$d=28.7^{\circ}-18.3^{\circ}=10.4^{\circ}$$

If we let $\ell$ be the side common to both triangles, we may use the law of sines to state:

$$\frac{\ell}{\sin\left(90^{\circ}\right)}=\frac{h}{\sin(c)}\implies h=\ell\sin(c)$$

$$\frac{\ell}{\sin(a)}=\frac{125\text{ ft}}{\sin(d)}\implies\ell=\frac{125\sin(a)}{\sin(d)}\text{ ft}$$

And so we find:

$$h=\frac{125\sin(a)\sin(c)}{\sin(d)}\text{ ft}\approx206.4\text{ ft}$$
 

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