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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Bisecting An Angle
Our goal is to draw the line that bisects the angle made by the blue, green and red points shown below.

First, draw a circle centered at the green point that goes through both line segments. To do so, select "Circle" from the choice menu in the lower left corner of the Applet. Click on the green point to select it as the center of the circle and then click anywhere else to create a point on the circle, making sure that this circle intersects both line segments.

Second, find the point of intersection of the circle and the two line segments. To do so, select "Intersect" from the choice menu, click on the circle and then click on one of the two line segments. Repeat for the other line segment.

Next, find the midpoint of the two points of intersection you just found. And finally, draw a line through the green point and the midpoint.

You have just drawn a line that bisects the appropriate angle. Can you explain why?