Geometry - finding radius of circle..

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  1. helpmee1234567890's Avatar
    • Exalted Member
    • Posts: 324
    Geometry - finding radius of circle..
    A circle is circumscribed about an isosclese triangle whose sides have lengths 13, 13, and 24cm

    Find the radius of the circle

    a diagram wasnt given but its basically a triangle with a circle around it

    I started of by finding the height of the triangle which is 5cm but i duno what to do next..

    any help?

    Thanks in advance
  2. TheMagicMan's Avatar
    • Overlord in Training
    • Posts: 3,015
    Re: Geometry - finding radius of circle..
    You are more likely to get a response here.

    Anyyhow, have you heard of the extended sine rule?

    Spoiler:
    Show
    the diameter of the circumcirlce is equal to the ratio of a side to the sine of an opposite angle. Combine this with the cosine rule
  3. dugdugdug's Avatar
    • Exalted Member
    • Posts: 375
    Re: Geometry - finding radius of circle..
    (Original post by helpmee1234567890)
    A circle is circumscribed about an isosclese triangle whose sides have lengths 13, 13, and 24cm

    Find the radius of the circle

    a diagram wasnt given but its basically a triangle with a circle around it

    I started of by finding the height of the triangle which is 5cm but i duno what to do next..

    any help?

    Thanks in advance
    I have worked out the answer to be 16.9

    If that agrees with the answer in your book, let me know and I'll send you the solution (hard to explain without showing you a drawing) but essentially it uses the fact that there's a right angled triangle in a semi-circle and pythagoras with simultaneous equations.
  4. helpmee1234567890's Avatar
    • Exalted Member
    • Posts: 324
    Re: Geometry - finding radius of circle..
    (Original post by dugdugdug)
    I have worked out the answer to be 16.9

    If that agrees with the answer in your book, let me know and I'll send you the solution (hard to explain without showing you a drawing) but essentially it uses the fact that there's a right angled triangle in a semi-circle and pythagoras with simultaneous equations.
    Hey
    yeh thats the answer I found it in the end but thanks
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