Drawing an Oval with a String and Three Nails
Drawing an Oval with a String and Three Nails
It is commonly known that you can draw a circle using a pencil, a nail, and a loop of string: moving the pencil around the nail while holding it taut against the loop maintains a constant radius around the nail, and the resulting figure is a circle with the nail at its center.
A similar procedure using a pencil and string with two nails maintains a constant sum of distances from the two nails, and the resulting figure is an ellipse with each nail at one focus of the ellipse.
Carrying out the same process with three nails results in an oval or egg shape.