July 22nd, 2008, 04:33 PM  #1 
Newbie Joined: Jul 2008 Posts: 10 Thanks: 0  Line tangent to a circle.
The line 3x + 4y  14 = 0 is tangent to the circle with center C ( 1, 2 ). How would you determine the radius of the circle algebraically? And write the equation of the circle?

July 23rd, 2008, 01:13 AM  #2 
Newbie Joined: Jun 2008 From: New Zealand Posts: 20 Thanks: 0  Re: Line tangent to a circle.
The radius of the circle is equal to the distance from the center (1, 2) to the line 3x + 4y  14 = 0. The distance from $\displaystyle (x_0 , y_0)$ to line $\displaystyle Ax + By + C = 0$ can be found by the formula: $\displaystyle D = \frac{Ax_0 + By_0 + C}{\sqrt{A^2 + B^2}}$ Last edited by skipjack; February 28th, 2018 at 12:53 PM. 

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circle, line, tangent 
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