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Precalculus Help

  1. Jan 25, 2005 #1
    I was wondering if anyone could help me with this problem

    A circle is tanget to line 2x-y+1=0, at point (2, 5), and the center point is on line, x+y=9. Determine the equation (in general form) of the circle.

    Normally I can do this sort of problem but I am having a hard time with this one. I don't know how to determine the center point or radius.....frustrating..

    Thanks, Jennifer
  2. jcsd
  3. Jan 25, 2005 #2
    This might be wrong because I'm basically an idiot, but here's what I'd do,…

    Write an equation for a line that is orthogonal to 2x-y+1=0 and also passes through point (2,5).

    Then solve for where that line and x+y=9 cross. That point must be the center of the circle.

    The radius of the circle is the distance between those two points and the rest is history, … Er,.. I mean, mathematics.

    I think that'll do it, but I'm sure some real mathematicians will come along and correct me if I'm wrong. :wink:
  4. Jan 25, 2005 #3


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    That's what I would've done.
  5. Oct 2, 2008 #4

    i just starting taking classes for pre-cal..... havent taken classes in yrs..... besides the calculator and the textbook - what else can i buy to help me with this class??? any tools?? (besides a tutor)

    Thanks in advance!

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