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Math Help - Finding the lengths and sides of a kite

  1. #1
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    Finding the lengths and sides of a kite

    Hello, Please advise if I have worked this lot out correctly.

    I have included a diagram to help explain what I am trying to do.

    Looking at the kite I require to find the length of the side BC. Apart from the angles included the only other information I was given is the length of the diagonal, which is 40cm

    I used the following idea

    a / sinA = b / sinB

    a / sin 25 = 40 / sin 100

    a = 40 sin 25 / sin 100

    a = 16.90 / 0.985 = 17.2 cm (3 sf)

    BC = 17.2 cm. This is the hypotenuse of the right hand lower triangle in the kite.

    I was asked to add a second diagonal BD and label the intersection. I know what an intersection is, but what do they mean by asking label it?

    Do they mean; ABD?

    I am required to find the length of the diagonal BD.

    This is what I did.

    I used the sin rule because when I look at the lower right hand side triangle, it is a right angle triangle and I have the angle opposite, so

    sin 50 x 17.2 = 13cm

    so the opposite side of the triangle length is 13cm

    I then used pythagoras to find the length of the adjacent side

    c = square root a^" - b^2

    17.2^2 - 13^2 = 11.3 cm

    Because I am asked for the length BD I have doubled it to 22.5 (3 sf)

    Please advise if I have worked it out OK

    Thanks

    David
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  2. #2
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    Re: Finding the lengths and sides of a kite

    Here are two very good webpages on the kite shape.

    PAGE ONE

    PAGE TWO
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  3. #3
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    Re: Finding the lengths and sides of a kite

    Thanks for the web pages, very well explained about kites, but no maths working out?
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  4. #4
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    Re: Finding the lengths and sides of a kite

    Quote Originally Posted by David Green View Post
    but no maths working out?
    But that is your job.
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  5. #5
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    Re: Finding the lengths and sides of a kite

    Quote Originally Posted by Plato View Post
    But that is your job.
    I agree, and I did it in my first thread, would of just liked a second professional opinion from somebody with more experience than I.

    David
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