It was a warm Saturday afternoon and the smell of fresh tortillas wafted through the Mexican restaurant. Scarcely had the food arrived before I roughly pushed my plate aside and began scribbling on a napkin at a feverish pace. "What are you doing?" asked my younger sister, raising an eyebrow and swallowing a mouthful of food. I mumbled something about Pythagoras and the tile floor. I don't know if my sister shrugged, rolled her eyes, or stuck out her tongue in response; I was too busy writing to look up. A minute or two later, I slammed my hand on the napkin dramatically. "Q. E. D.!" I declared aloud. My parents gave me an inquisitive look before continuing their meal. I picked up my burrito and took a large triumphant bite. My entire face glowed with a secret delight. I was 14 years old, and I had just found a new proof for the Pythagorean Theorem...