How to Build a Parabola
If one were to construct a y-axis and x-axis as imperfectly diagrammed by placing equidistant points along the axes and numbering them in the following way:
| points on the axes are to be equidistant
. --. --. --. --. --. --. --. --. --. --.
10 09 08 07 06 05 04 03 02 01
One can take a pine board and drive small nails equally spaced along the axes at the numbered points as shown, and then by extending straight lengths of wire to connect the 01, 02, 03... on the x-axis to its counterpart on the y-axis, (notice the reverse order on the x-axis) one may build a nice parabola.
The resulting wire lengths represent the tangents to the generated curve. If one were to increase the number of points on each axis let's say by doubling their number so that the numbers on the y-axis ran 01,02...,19,20 and those on the x-axis ran 20,19,...,02,01, and then connect them there would be more tangents and the parabola more perfectly described. Makes a suitable toy for idiots.
Here is something to waste some time with:
Represent every counting number from zero to twenty using four fours and any math symbol.
2 = (4 x 4)/(4 + 4)
Always use no fewer than four four's and no more.