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Perimeter of a triangle which circumscribes by 3 circles

  1. Apr 22, 2009 #1
    Hello, I need help with this problem plz (this is counted as large part of my grade so plz hel) thank you

    Problem:
    Each of three congruent circles has radius 1, and each is externally tangent to the other two. An equilateral triangle circumsribes this configuration, so that each circle is tangent to two of the sides of the triangle. What is the perimeter of the equilateral triangle?

    Here is my diagram. Please excuse me of my badly drawing scale TT

    http://www.freeimagehosting.net/uploads/4a1d944fce.jpg
     
  2. jcsd
  3. Apr 23, 2009 #2

    tiny-tim

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    Hi Paradiselovek! :smile:

    Show us how far you get, and where you're stuck, and then we'll know how to help!

    Hint: whenever you see tangent circles, draw the lines connecting their centres! (in this case, making a triangle) :wink:
     
  4. Apr 23, 2009 #3
    Well you see, i'm really stuck in this problem. I have no idea where to start to find the perimeter. I'm not asking for step by step but can you please help me by giving hints on those steps?thanks

    here what I did like you said:
    http://www.freeimagehosting.net/uploads/cccd0e11fa.jpg
     
  5. Apr 23, 2009 #4

    HallsofIvy

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    One thing you can get easily is the perimeter of that inner triangle. Can see what the ratio of "large triangle to small triangle" must be?
     
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