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Thread: Trig

  1. March 30th 2006, 03:34 AM #1
    classicstrings
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    Trig

    Stuck on this one...

    The perimeter of a parallelogram is 44cm and the length of the shorter diagonal is 14cm. Find the lengths of the sides, given that they contain an angle of 60 degrees.

    And this...

    THe angles of elevation of the top of a tower from the top of a building 100m high are 50 and 75 respectively. FInd the height of the tower.

    I drew diagrams but it still wont work out!
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  2. March 30th 2006, 04:41 AM #2
    earboth
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    Quote Originally Posted by classicstrings
    Stuck on this one...

    The perimeter of a parallelogram is 44cm and the length of the shorter diagonal is 14cm. Find the lengths of the sides, given that they contain an angle of 60 degrees.
    And this...

    THe angles of elevation of the top of a tower from the top of a building 100m high are 50 and 75 respectively. FInd the height of the tower.

    I drew diagrams but it still wont work out!
    Hello,

    I've attached a drawing.
    1. two neighbored sides form a triangle together with the short diagonal.
    To calculate the sides you have to use the Cosine Rule:
    14^2=x^2+(22-x)^2-2 \cdot x \cdot (22-x) \cdot \cos(60^{\circ})

    with \cos(60\circ})=\frac{1}{2} you'llget a quadratic equation:
    3x^2-66x+288=0 and the solutions for x= 16 or x= 6.

    Next problem will follow. Now I'm in a hurry.

    Greetings

    EB
    Attached Thumbnails Attached Thumbnails Trig-parallgr1.bmp  
    Last edited by earboth; March 30th 2006 at 04:42 AM. Reason: add drawing
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  3. March 30th 2006, 06:35 AM #3
    earboth
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    Quote Originally Posted by classicstrings
    Stuck on this one...

    ...
    THe angles of elevation of the top of a tower from the top of a building 100m high are 50 and 75 respectively. FInd the height of the tower.

    I drew diagrams but it still wont work out!
    Hello,

    I'm awfully sorry, but are you sure that this is the complete problem? There must be at least one value (or another point) to calculate the height.
    Please attach your diagrams. Maybe that will help me to help you.

    Greetings

    EB
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