An applet for demonstrate the loci formed by a point on slid
A ruler with a marked point slides in a coordinate system. When the point is located at the midpoint of the ruler, then the point moves on the arc of a circle, while the ruler slides. When the point is located somewhere else, then the point moves on the arc of an ellipse, while the ruler slides. The location of the ellipse's foci on the system axes, depends on the location point on the ruler.