[color=#0000ff][b]Hippias of Elis[/b][/color] (460 - 400 BC) was a statesman and a philosopher. His only contribution to mathematics is the invention of Quadratrix of Hippias - a special curve that can be used for squaring a circle.[br][br]Quadratrix of Hippias can be obtained as follows:[br][br]Let ABCD be a unit square. Using the slider in the above diagram to change the value of t from 0 to 1, the red line segment will rotate about B and the blue line segment will slide down, both at constant speed. The intersection point F will trace out the Quadratrix of Hippias. Check the box to show the curve.[br][br]When [math]t=1[/math], [math]FB=\frac{2}{\pi}[/math], from which the length [math]\pi[/math] can be constructed easily by straightedge and compass.