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Math Help - area of triangles 2

  1. #1
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    Exclamation area of triangles 2

    a rhombus has an area of 50 cm^2 and an internal angle of size 63 degrees. Find the lenth of its sides.

    please show all working out.
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  2. #2
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    Quote Originally Posted by Tessarina View Post
    a rhombus has an area of 50 cm^2 and an internal angle of size 63 degrees. Find the lenth of its sides.

    please show all working out.
    ... use the parallelogram area formula provided in your previous post.
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  3. #3
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    i worked out the other one, but with this one i just can't seem to get the right answer.

    i think iam doing something wrong,
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  4. #4
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    Quote Originally Posted by Tessarina View Post
    i worked out the other one, but with this one i just can't seem to get the right answer.

    i think iam doing something wrong,
    can't fix it if we don't know what you tried ...
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  5. #5
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    could you just show me what working out you would do?
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  6. #6
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    Try using the formula

    A = ab\sin{\theta}.


    Like Skeeter said, show us what working you have done. We are not here to do your work for you.
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  7. #7
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    this is the working out i did:

    A= 50cm^2

    1/2 x a x c x sin63= 50

    acsin63= 100


    -and thats all i got to.
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    Quote Originally Posted by Tessarina View Post
    this is the working out i did:

    A= 50cm^2

    1/2 x a x c x sin63= 50

    acsin63= 100


    -and thats all i got to.
    You're almost there. Just remember that in a rhombus, all sides are equal.
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  9. #9
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    then do i work it out by going--
    2asin63=100
    2a=100/sin63
    2a=112.23
    a=56.11

    but then if i double that to get the area of the whole rhombus i get
    112.23

    which is the wrong answer.
    the answer is: 137.0cm^2

    what am i doing wrong?
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  10. #10
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    Quote Originally Posted by Tessarina View Post
    then do i work it out by going--
    2asin63=100
    2a=100/sin63
    2a=112.23
    a=56.11

    but then if i double that to get the area of the whole rhombus i get
    112.23

    which is the wrong answer.
    the answer is: 137.0cm^2

    what am i doing wrong?
    It should actually be

    a^2\sin{\theta} = 100.


    BTW you only halve when you are finding the area of a triangle. Since it's half of a parallelogram.
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  11. #11
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    then it would be-

    a^2= 100/sin63
    a= 10.59

    so if that is the length of one side, how do i then work out he are of the entire rhombus?
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  12. #12
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    Quote Originally Posted by Tessarina View Post
    then it would be-

    a^2= 100/sin63
    a= 10.59

    so if that is the length of one side, how do i then work out he are of the entire rhombus?
    Oops, it should have actually been

    a^2\sin{63^{\circ}} = 50.


    You already know the area of the rhombus, it's 50\,\textrm{cm}^2. You're trying to find the side length, i.e. a.
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  13. #13
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    I got it!
    Thank you so much.

    i realised then that i was looking at the wrong answer in the back of the book, thats why it wasnt making sense.

    Thank you
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