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Thread: Please help with a trig optimization word problem.

  1. #1
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    Please help with a trig optimization word problem.

    I'm not even sure what the diagram would look like for this:

    A ladder 9m long is to be moved horizontally around a 90 degree corner from one corridor 2.5m wide into a second corridor. How narrow can the second corridor be and still permit the ladder to go around the corner? Neglect the width of the ladder.

    The answer is 3.92m. Thanks in advance!
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  2. #2
    SGS
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    Re: Please help with a trig optimization word problem.

    Quote Originally Posted by pereeia View Post
    I'm not even sure what the diagram would look like for this:

    A ladder 9m long is to be moved horizontally around a 90 degree corner from one corridor 2.5m wide into a second corridor. How narrow can the second corridor be and still permit the ladder to go around the corner? Neglect the width of the ladder.

    The answer is 3.92m. Thanks in advance!
    You can't neglect the width of the ladder!

    It depends on if you hold the ladder so the rungs are horizontal or vertical.
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    Re: Please help with a trig optimization word problem.

    It says you're carrying the ladder horizontally, so the ladder would be on its side if that makes sense.
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    Re: Please help with a trig optimization word problem.

    Quote Originally Posted by pereeia View Post
    I'm not even sure what the diagram would look like for this: A ladder 9m long is to be moved horizontally around a 90 degree corner from one corridor 2.5m wide into a second corridor. How narrow can the second corridor be and still permit the ladder to go around the corner? Neglect the width of the ladder. The answer is 3.92m.
    Quote Originally Posted by SGS View Post
    You can't neglect the width of the ladder!
    It depends on if you hold the ladder so the rungs are horizontal or vertical.
    Only the length matters.
    Look at the diagram.Please help with a trig optimization word problem.-untitled.gif

    BTW. I once was at a University where the civil engineers of all people built a new building. Then they had custom made cabinets done. But the cabinets could not be moved in because they would not round the corners. Those of us who taught their students calculus had great fun when coming to this very question.
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  5. #5
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    Re: Please help with a trig optimization word problem.

    Quote Originally Posted by Plato View Post
    Only the length matters.
    Look at the diagram.Click image for larger version. 

Name:	Untitled.gif 
Views:	0 
Size:	2.3 KB 
ID:	37415

    BTW. I once was at a University where the civil engineers of all people built a new building. Then they had custom made cabinets done. But the cabinets could not be moved in because they would not round the corners. Those of us who taught their students calculus had great fun when coming to this very question.
    This is of course correct for this problem.

    In real life you can also rotate the ladder parallel to the walls and gain a fair bit more leeway.

    I know this from having done painting and having had to move ladders all over the place in narrow corridors.
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    Re: Please help with a trig optimization word problem.

    Quote Originally Posted by Plato View Post
    Only the length matters.
    Look at the diagram.Click image for larger version. 

Name:	Untitled.gif 
Views:	0 
Size:	2.3 KB 
ID:	37415

    BTW. I once was at a University where the civil engineers of all people built a new building. Then they had custom made cabinets done. But the cabinets could not be moved in because they would not round the corners. Those of us who taught their students calculus had great fun when coming to this very question.
    Thanks man. I managed to solve the question thanks to your diagram.
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    Re: Please help with a trig optimization word problem.

    Quote Originally Posted by romsek View Post
    This is of course correct for this problem.
    In real life you can also rotate the ladder parallel to the walls and gain a fair bit more leeway.
    I know this from having done painting and having had to move ladders all over the place in narrow corridors.
    Well try that with 600 lb. cabinets that are 11 meters long.
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