Stage: 4 Challenge Level: 
A square paper napkin is folded so that the corner P coincides with the midpoint of an opposite edge as shown in the diagram.
Investigate the three triangles that are formed by folding in this way (where there is a single thickness of the paper).
Scale factors. Long problems. Cosine rule. Circles. Pythagorean triples. Area. Fractal. Mathematical reasoning & proof. Pythagoras' theorem. Similarity.
Published March 2000,January 2009.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk
