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Calc III

  1. Feb 2, 2009 #1
    1. The problem statement, all variables and given/known data

    Write the equation of the sphere whose diameter has endpoints at (-1,1,-3) and (3,-1,2).



    2. Relevant equations



    3. The attempt at a solution

    (x-x1)2+ (y-y1)2+ (z-z1)2= r2

    the center of the sphere is : (1,0,-1/2)
    r= [tex]\sqrt{}5/4[/tex]

    then the equation is: (x-1)2+(y-0)2+(z+1/2)2=5/4

    Please someone check my answer and if I am not right, help me to solve it.
     
  2. jcsd
  3. Feb 2, 2009 #2

    tiny-tim

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    Hi mamma_mia66! :smile:

    Centre is right. :biggrin:

    But r is wrong. :cry:

    (you've calculated the distance from the centre to the origin! :wink:)
     
  4. Feb 2, 2009 #3
    I am not sure that I know how to find the r ???? too old to remember it after so many years not being in school.
     
  5. Feb 2, 2009 #4

    tiny-tim

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    Yes you do! :biggrin:

    they've given you a diameter:wink:
     
  6. Feb 2, 2009 #5
    r= sq. rt. (3-1)2+ (1-0)2+(2-1/2)2= 21/4
     
    Last edited: Feb 2, 2009
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