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Math Help - how can I solve this story problem?

  1. #1
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    how can I solve this story problem?

    The shadow of a flagpole installed at an angle 5 degrees away from the sun casts a 30mshadow when the sun is 15 degrees above the horizon. How tall is the flagpole? thanks guys in advance for any help
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  2. #2
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    Re: how can I solve this story problem?

    I take it you mean pole is 5 degrees to the vertical. In that case sketch a diagram and look at the triangle with sides shadow,flagpole and a ray of the sun. You can then use sine rule to get the length of the flagpole.
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  3. #3
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    Re: how can I solve this story problem?

    Quote Originally Posted by Sportsman View Post
    The shadow of a flagpole installed at an angle 5 degrees away from the sun casts a 30mshadow when the sun is 15 degrees above the horizon. How tall is the flagpole? thanks guys in advance for any help
    How in heck can the sun be 15 degrees above the horizon?

    Very unclear...either 5 degrees or 15 degrees at top of flagpole...
    5 degrees: f = 30SIN(85) / SIN(5)
    15 degrees: f = 30SIN(75) / SIN(15)
    If you don't "get that", look up the Law of Sines.

    AND: any reason for you to call this a "story problem"?
    I notice that this term is used more often than Carter has liver pills !
    Last edited by Wilmer; April 3rd 2012 at 09:49 AM.
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  4. #4
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    Re: how can I solve this story problem?

    It means the sun's rays make an angle of 15 degrees with the ground. It is called the angle of elevation of the sun.
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  5. #5
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    Re: how can I solve this story problem?

    Quote Originally Posted by biffboy View Post
    It means the sun's rays make an angle of 15 degrees with the ground. It is called the angle of elevation of the sun.
    OK; good nuff...
    But here's the problem as posted:
    "The shadow of a flagpole installed at an angle 5 degrees away from the sun
    casts a 30mshadow when the sun is 15 degrees above the horizon."

    So we have a right triangle with one of legs = 30.
    What are the angles: 5:85 or 15:75 ? Or something else? "5 degrees away" means what?
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  6. #6
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    Re: how can I solve this story problem?

    My triangle has a base (AB) of 30. The third vertex is C. CA represents the suns ray, so angle CAB=15 degrees. CB represents the flagpole. It is at an angle 5 degrees to the left of the vertical.
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  7. #7
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    Re: how can I solve this story problem?

    Well...
    If I was the principal of a school where problems that took longer to decipher
    than to solve were made up by a teacher...I'd fire that teacher!
    It's evident that the student here is learning right triangles associated with the
    Law of Sines...why not just give him a triangle with a given angle and a given side...
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  8. #8
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    Re: how can I solve this story problem?

    Quote Originally Posted by Wilmer View Post
    Well...
    If I was the principal of a school where problems that took longer to decipher
    than to solve were made up by a teacher...I'd fire that teacher!
    It's evident that the student here is learning right triangles associated with the
    Law of Sines...why not just give him a triangle with a given angle and a given side...
    This whole thing could've been settled easily if OP had attached a drawing.
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  9. #9
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    Re: how can I solve this story problem?

    Quote Originally Posted by masters View Post
    This whole thing could've been settled easily if OP had attached a drawing.
    True; but I'm sure he/she didn't have such an animal, else he/she would not have asked for help.
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  10. #10
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    Re: how can I solve this story problem?

    Quote Originally Posted by Wilmer View Post
    OK; good nuff...
    But here's the problem as posted:
    "The shadow of a flagpole installed at an angle 5 degrees away from the sun
    casts a 30mshadow when the sun is 15 degrees above the horizon."

    So we have a right triangle with one of legs = 30.
    No, there is NO right triangle. The problem is very clear that one side of the triangle has length 30 m, one angle on that leg 90- 5= 85 degrees and the other 15 degrees. The third angle is, of course, 180- 85- 15= 80 degrees. You can use the sine law to solve for the lengths of the flag pole: x/sin(15)= 30/sin(100).
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  11. #11
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    Re: how can I solve this story problem?

    You call this very clear:
    "The shadow of a flagpole installed at an angle 5 degrees away from the sun
    casts a 30mshadow when the sun is 15 degrees above the horizon." ?!

    The only thing that's clear here is "30m shadow".

    If I install a fence post non-vertically, I don't say: my post is x degrees away from the sun...

    If anybody thinks it's "normal" for a teacher to make up such a problem when the poor
    student is learning about triangles and angles, well then....

    Even Biffboy wasn't sure:
    "I take it you mean pole is 5 degrees to the vertical. In that case..."
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