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Appendix C C-101<br />
MINI PROJECT 2<br />
Constructing a Parabola<br />
This hands-on mini project shows you how to construct a parabola. Follow the<br />
instructions, and then explain why the curve that you draw is indeed a<br />
parabola. In addition to a sheet of paper and a pen or marker, you’ll need the<br />
following:<br />
• A T-square and a drawing board or surface on which you can easily slide the<br />
T-square left and right in a straight horizontal path<br />
• A piece of string that has the same length as the long bar of the T-square (see<br />
Figure C)<br />
• Two thumb tacks<br />
(Refer to Figure D.) Tack one end of the piece of string to a point on the drawing<br />
board. Call that point F. Tack the other end of the string to the top right<br />
corner of the T-square, as indicated in Figure D. Now, with the pen or marker,<br />
move the T-square horizontally subject to the following two constraints:<br />
The string<br />
Piece of string with<br />
same length as long<br />
bar of T-square<br />
F<br />
T-square<br />
Figure C<br />
Figure D<br />
must be kept taut by the pen, and the pen must stay against the edge of the<br />
T-square. The curve traced out by the pen will be a portion of a parabola. (In<br />
practice, the piece of string that you begin with should actually be just slightly<br />
longer than the length of the T-square, since a slight amount of the string is<br />
taken up in the tacking.)