I have used Geoboard for iPad to visualize
the Pythagorean theorem proof by Leonardo da Vinci check out a variety of conjectures.
You can download
Download on the App Store: Geoboard, by The Math Learning Center - Clarity Innovations.
Geoboard, by The Math Learning Center
The Geoboard is a mathematical manipulative tool for exploring a variety of
basic concepts in plane geometry introduced in the elementary and middle grades. Learners stretch bands around pegs to form line segments and polygons and make discoveries about perimeter, area, angles, congruence, translation,
scaling,, fractions, and more.
This virtual version of the manipulative is an open-ended educational tool, ideal for elementary classrooms and other learning environments that use iPod Touches, iPhones, or iPads.