geometry anyone?

Discussion in 'General' started by OneSeventeen, 29 Sep 2003.

  1. OneSeventeen

    OneSeventeen Oooh Shiny!

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    I've got a triangle, and I know two sides and an angle...
    I need to find the other 2 angles and the other side...
    [​IMG]
    I feel stupid for asking, but I'm a bit out of it, and haven't taken a math class in a while... A year ago I did this stuff in my sleep, but now if it doesn't have a right angle, I'm lost :(

    (please wait until I'm gone to call me stupid! :p)

    EDIT:: I'm going for any angles/sides as long as they work, I know there is more than one solution
    EDIT2:: We're trying to disprove "Side Side Angle" I know Side Angle Side proves triangles are congruent, but Side Side Angle doesn't. (hope that helps and doesn't just confuse things!)
     
  2. VadimtheConqueror

    VadimtheConqueror I love the little tacos...

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    c/sin(c)= b/sin(b)

    5/sin(93)=3/sin(b)

    sin(b)*( 5/sin(93))=3

    sin(b)=3sin(93)/5

    sin(b)=0.5991

    b=36.8 degrees

    180-a-b-c=0
    180-b-c=a
    180-93-36.8=a
    50.2=a


    A/sin(a)=B/sin(b)
    A=Bsin(a)/sin(b)

    A=3sin(50.2)/sin(36.8)
    A=3(0.7683)/0.5991
    A=3.85




    sorry, i'm bored
     
  3. OneSeventeen

    OneSeventeen Oooh Shiny!

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    unfortunately those are the numbers I started with (sorry, I should have mentioned that!)

    There is a second set of numbers that should work, but I figured it out... I used AutoCAD, zoomed in & eyeballed it, and turned down precision... :p the math works out close enough to get by tomorrow! :D
     
  4. VadimtheConqueror

    VadimtheConqueror I love the little tacos...

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    bah! oh well, i was bored, gave me something to do for a bit.
     
  5. OneSeventeen

    OneSeventeen Oooh Shiny!

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    you're welcome to figure out/explain how to find out the second set of numbers... :p

    j/k
     
  6. Astrum

    Astrum Dare to dream.

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    Oh boy, this is going to be a LONG post...

    Going from Vadim's post:
    a = 50.2
    A = 3.85
    b = 36.8

    Let's start with angle b. We know that sine is positive in the first and second quadrant, so when we solve for be in this equation we can come up with a second value:

    B/sin(b) = C/sin(c)
    3/sin(b) = 5/sin(93)
    b = 36.8 or 180 - 38.8 = 143.2
    We can prove this works:
    3/sin(143.2) = 5/sin(93)
    5 = 5

    so b = 36.8 && 143.2

    From that we know that a = 50.2 && -56.2

    So side from there we find A using the second angle:
    A/sin(-56.2) = 3/sin(143.2)
    A = -4.2

    so A = 3.85 && -4.2

    I'm sure something is wrong in that but those are all technically right.
     

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