On Jan 6, 2005, at 8:40 AM, James Hurley wrote:
What is the perpendicular distance between a point and a line?
I was grading my daughter's math papers and thought of a couple things related to this.
1. It is possible to create the general line parameters A, B and C of Ax + By + C =0 without any division, so no 'if' is needed. This can be normalized by dividing by sqrt( A^2 + B^2 ), and since both A and B can't be 0 (assuming the two points defining the line are not identical), there is no division by zero here either.
2
If you save the line description in normal form at mouse down then you can calculate the distance at mouseMove faster. It is simply Ax + By + C, where (x,y) is the point of interest. This is the normalized A, B, & C where A = cos(omega) etc., the form you mentioned in other mail.
Dar Scott
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