trig question

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M

mjrand

Senior member
Dec 12, 1999
412
0
76
Been a few years since I last looked at trig and now I'm trying to relearn it. I'm up to a problem though that has got me stumped. I'm not so much looking for the answer here, rather the process to get the answer as I truly want to learn how to do this stuff myself.

"A ladder is placed against a wall, with its base 2 m from the wall. The latter touches the top of a 2 m fence that is 1.5 m from the wall. How high up the wall does the latter reach?"

Anyone have any idea how I would figure this out?

Thanks
 
M

mjrand

Senior member
Dec 12, 1999
412
0
76
MCrusty, you have me totally confused. :/

Lynx516, I actually have a diagram. I just don't understand what the question is asking exactly. It says directly in the question that the ladder touches the top of a 2m fence. So does that mean the ladder is 2m high or do I have no clue what its asking?
 
L

Lonyo

Lifer
Aug 10, 2002
21,938
6
81
I didn't get what the question was asking either. Is what is in your post the exact wording of the question? If so, the question is as confusing as hell.
 
J

JoeKing

Lifer
Oct 9, 1999
10,641
1
81
I'm usually realy good with trig, but that question is plain confusing. Where the hell does the fence come from?
 
H

Heisenberg

Lifer
Dec 21, 2001
10,621
1
0
That's a badly worded question. I think that the fence is between the ladder and the wall. So the ladder is basically on top of the fence as it leans.
 
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johnjbruin

Diamond Member
Jul 17, 2001
4,401
1
0
find the angle. Then use tangent(angle) = (height where ladder reaches top) / ( how far the ladder is)

To clarify: I think it means this:

ladder is 2m away from the wall
fence is in the middle of the two.
fence is 1.5m aways from wall
the ladder leans on the fense which is 2m tall.
so how far up is the ladder going on the wall?
 
M

mjrand

Senior member
Dec 12, 1999
412
0
76
johnjbruin, thanks for making the question a bit more clear.

I still don't understand why the distances from the wall make any difference though. Why does the question tell me the fence is 1.5m from the wall and the ladder is 2m from the wall..in what way do these variables affect the height of the ladder? Couldn't it just say that theres a wall and a fence next to the wall and the ladder which is 2m tall is on top of the fence which is 1.5m tall?
 
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johnjbruin

Diamond Member
Jul 17, 2001
4,401
1
0
|\
| \
| . \
| . | \
| . | . \

<-1.5-><-00.5->

wall - fence - ladder
at 0 - at 1.5 - at 2


PS. Ignore dots used for spacing
 
J

johnjbruin

Diamond Member
Jul 17, 2001
4,401
1
0
Originally posted by: mjrand
I made a picture in paint that basically looks like the picture in my book.

http://www.bbcc.ca/hosted/gallery/albums/userpics/trig%7E0.JPG

It looks similar to yours johnjbruin, but I'm still not sure how to get the height of the ladder as I don't have either the height or length of the wall. Am I missing something?
Click to expand...

If for every 0.5 meters you get 2 meters of height... then for a total of 2 meters you get total heght =

total height / total distance = 2m / 0.5m

or you get 8m for the total height...

this was more of a similar triangles problem rather than trig... but trig could also be used to solve this... refer to my finding angle and using tangent method from earlier.
 
V

Venix

Golden Member
Aug 22, 2002
1,084
3
81
As other posters have said, "similar triangles". There is a small triangle with a base of .5 meters and a height of 2 meters, and a big triangle with a base of 2 meters and a height of x meters. You need to solve for x.
 
M

mjrand

Senior member
Dec 12, 1999
412
0
76
Hmm so the ladder is the big triangle? I thought the whole time that it was the small one and that the fence was the big one and it was between the ladder and the wall. Ok I now understand how you got the answer, but the question still seems confusing. It says "the ladder touches the top of a 2m fence". This doesnt mean anything to me as I don't understand what it means. A ladder can't possibly be sitting on top of a fence. That's impossible.
 
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johnjbruin

Diamond Member
Jul 17, 2001
4,401
1
0
Originally posted by: mjrand
Hmm so the ladder is the big triangle? I thought the whole time that it was the small one and that the fence was the big one and it was between the ladder and the wall. Ok I now understand how you got the answer, but the question still seems confusing. It says "the ladder touches the top of a 2m fence". This doesnt mean anything to me as I don't understand what it means. A ladder can't possibly be sitting on top of a fence. That's impossible.
Click to expand...

Agreed... that was a pretty sh!tty description. But if they gave you that picture in your book... it should have been pretty ok.
 
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