Copia de Proof Without Words

Drage the points. Drag the slider. What does this prove? How does this prove?
Based on http://45.media.tumblr.com/9e608e03763922f7620fa7b21487f640/tumblr_nywxpgk6631uk13a5o1_500.gif
– natasciatabarrini, Steve Phelps

Information: Copia de Proof Without Words