Drag point R - try moving it along the red line segment or along other grid lines, or on the grey or yellow circle. Can you find any patterns? This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com Use the RESET button, top right, to clean the page.
Created with GeoGebra
M-A1