perpendicular line from a point to line

[Thirumalyara]

Hi,

can any one help me ....

i am having a line with (x1,y1) and (x2,y2) and a point (x3,y3).  i need to draw a line from (x3,y3) to the line with 90 degrees. so that it touches on line at a point (x4,y4). how we can find his point (x4,y4) .


thanks in advance ....

regards
thirumal y

[BrentHoskisson]

This page has everything you need.

http://a-levelmathstutor.com/straight-lines.php

Basically it's example 2 in the middle of this page.