Inscribed Quadrilaterals Theorem (Cyclic Quadrilaterals)
Any quadrilateral that is inscribed inside a circle is said to be a cyclic quadrilateral.
In the applet below, a cyclic quadrilateral (with movable vertices) is shown.
Slide the slider slowly and carefully observe what happens. Then, reset the applet.
Change the locations of the BIG POINTS and repeat this process.