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Math Help - please help, quadrilateral

  1. #1
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    please help, quadrilateral

    Hi people

    I have to work out the area and diagonals of a quadrilateral,
    the side lengths are AB = 19.4, BC = 27.6, CD= 16.9, DA= 213 and
    angle B = 65 degrees
    can anybody help with the calculations/ answer as im completely stumped,
    any advise would be greatly appreciated

    thanks John
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  2. #2
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    Quote Originally Posted by ratherbsurfing View Post
    I have to work out the area and diagonals of a quadrilateral,
    the side lengths are AB = 19.4, BC = 27.6, CD= 16.9, DA= 213 and
    angle B = 65 degrees
    Start by drawing the diagonal AC. You can then use the cosine rule to find the length AC and then the angles in the triangles ABC and ACD. The area of the quadrilateral is the sum of the areas of the two triangles (which you get from the formula " \tfrac12ab\sin C"). Finally, draw the other diagonal BD and get its length by using the cosine rule in the triangle BCD (because by then you will know the angle at C: it is the sum of the angles ACB and ACD).
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  3. #3
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    Opalg

    thats brilliant thanks Ill give it a try, think ill still struggle but here goes

    thanks John
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  4. #4
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    Please note that this is not an advanced geometry question thus it belongs in the pre-university forums, not the university forums.
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