Angle of Elevation.. Again.

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Mathisconfusing101

Junior Member
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Jun 19, 2006
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I don't think I am doing this right.

A tower stands at a height of 45 meters. A point lies 12 meters from the base of the lighthouse. Find the angle of elevation.

so that would be opp over adj.

so 25/12... which gives me 3.75.

My calculator is in the degrees mode..

but 3.75 is not one one the answer choices

a. 75° b. 60° c. 15°

what am I doing wrong?

Do I have to do tan3.75 to get the answer?
 
Mathisconfusing101 said:
Do I have to do tan3.75 to get the answer?
Click to expand...
Since "3.75" represents the tangent of the angle, and since you were asked for the measure of that angle, yes, you would need to work backwards, using the inverse-trig function, to find the angle measure.

Using units on your work can help you notice things like this. Dividing meters by meters gives a dimensionless value, but your answer needs to have the dimension of "degrees". So the fact that "3.75" has no dimension tells you that this must not be the final answer.

Hope that helps a bit.

Eliz.
 
Mathisconfusing101 said:
I don't think I am doing this right.

A tower stands at a height of 45 meters. A point lies 12 meters from the base of the lighthouse. Find the angle of elevation.

so that would be opp over adj.

so 25/12... which gives me 3.75.

Alas, Poor Mathisconfusing101.

\(\displaystyle \L\\tan^{-1}(\frac{45}{12})\ or\ cot^{-1}(\frac{12}{45})\)

You seem to be having a rough time with these concepts.

Since the distance from the tree to you is shorter than the height of the tree, you will have a larger angle than if you were at the top of the tree looking down at the 12 foot point.

Let's suppose you were in the top of the tree and wanted to know the angle to the 12 away point. That would just be 90-75=15, thereabouts.

That would be \(\displaystyle \L\\tan^{-1}(\frac{12}{45})\ or\ cot^{-1}(\frac{45}{12})\)

See?. Just the opposite, so to speak, of the way we used to find the other angle. All of these trig operations are tied together. I think once it clicks you're going to see how easy it is.

My calculator is in the degrees mode..

but 3.75 is not one one the answer choices

a. 75° b. 60° c. 15°

what am I doing wrong?

Do I have to do tan^(-1)3.75 to get the answer?
Click to expand...
 
NO. Why do you insist on making these problems so difficult? Where did "25" come from? the tower's height is 45.

let \(\displaystyle \theta\) be the angle of elevation.

\(\displaystyle \theta = tan^{-1}(45/12)\)

\(\displaystyle \theta = 75 degrees\)

answer (a). :roll:
 
skeeter said:
NO. Why do you insist on making these problems so difficult? Where did "25" come from? the tower's height is 45.

let \(\displaystyle \theta\) be the angle of elevation.

\(\displaystyle \theta = tan^{-1}(45/12)\)

\(\displaystyle \theta = 75 degrees\)

answer (a). :roll:
Click to expand...

Mathisconfusing101 was told to seek real life tutoring, and after reading the past couple of posts made by this individual, I strongly RECOMMEND it.
 
Mathisconfusing101 said:
ok. um. when i do that.. i get .06554.... etc.

sry if this sounds repetitive or dumb... but... now what? *sigh*
Click to expand...

Sounds like you didn't enter this correctly in your calculator.

Make sure your calculator is set in "degree" mode (which you said yours is).

Key in

2nd Tan 3.75 [enter]

See what you get.
 
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