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Math Help - Analytic Geometry - Circle

  1. #1
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    Analytic Geometry - Circle

    Find the equation of a circle passing through (3,7) and tangent to the lines x - 3y + 8 = 0 and y = 3x.

    Please help me and show the solution... Thanks!
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  2. #2
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    Quote Originally Posted by lance View Post
    Find the equation of a circle passing through (3,7) and tangent to the lines x - 3y + 8 = 0 and y = 3x.

    Please help me and show the solution... Thanks!
    for the circle x^2+y^2+2gx+2fy+c=0-----(1) the equation of the tangent at the point (x1,y1) is xx1+yy1+2g(x+x1)+2f(y+y1)+c=0(this is given in textbooks if you ask me how).comparing the given equations with this equation you will get the 2 points (x1,y1)=(1,-3) and (x2,y2)=(3,-1). so u have 3 points and 3 equations in f,g,c by putting the points in (1). you should get the answers therefore.
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