
Circle and tangents

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Substitute in the equation for the circle. You will get a quadratic equation for x. Write down the condition for this quadratic to have equal roots. That will give you an equation for m.

I have another way if that's OK.
By completing the square, we find the circle has equation
The tangent line will be a distance from the center of the circle equal to the radius length of . The center of the circle is at (1,2)
Using the distance between a line and a point formula:
Solving for m gives


Quote:
Originally Posted by
Soroban
Hello : THANK YOU
All lines with the equation http://www.mathhelpforum.com/mathhe...7a4296701.gif pass through the point P(4,0)AND NOT TANGENT IN THE POINT.