David Little
Mathematics Department
Penn State University
Eberly College of Science
University Park, PA 16802
Office: 403 McAllister
Phone: (814) 865-3329
Fax: (814) 865-3735

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Projecting A Point Onto A Line
Our goal is to find the point on the line through the red and blue points that is closest to the green point.

First, we will draw the line through the green point that is prependicular to the line. To do so, select "Perpendicular Line" from the choice menu and follow the instructions. Or you can construct this line manually (see Constructing a Perpendicular Line).

Now find the intersection of the two lines. This is the point we were looking for! Can you explain why?