Could someone please explain how the implict line. I have a book that

explains how to determine the center point of a circle with radius r and

tangent to two intersecting lines. However it's pseudocode code explains in

the form of lines being implict form. I.E. they use

ax + by +c =0 as the line definition. Now, if I have the points p1(x,y) and

p2(x,y)

which define the line L0 in affine space and points p2(x,y) and p3(x,y)

which forms line L1 and intersects line L0, where are they getting the a, b

and c values for each of the lines.

Now, in the book "Geometric Tools for Computer graphics" it explains the

elements as being:

The alorithm they use is as follows:

struct Line2D

{

double x,y,a,b,c;

void CircleTangentToLinesGivenR(Line2D L1,Line2D L2, double radius, Point &Quote:}

center[4])

{

double discrm0 = sqrt(L1.a*L1.a + L1.b*L1.b) * r;

double discrm1 = sqrt(L2.a*L2.a + L2.b*L2.b) * r;

double invDenom = 1.0/(-L2.a*L1.b + L1.a*L2.b);

center[0].x = -(L2.b*(L1.c+discrm0)-)...

Quote:}