Task: Text Categorization
Input (English): E. S. Loomis published a compendium about this statement, which Edsger Dijkstra generalized using the signum function. Generalized to inner product spaces, this statement is Parseval's identity, while its analog in three dimensions is de Gua's theorem. Euclid's proof of it, like many others, uses a figure known as the bride's chair. This statement is logically equivalent to Euclid's parallel postulate, and its generalization to powers higher than two, proved unsolvable by Andrew Wiles, is Fermat's last theorem. For 10 points, name this special case of the law of cosines, a statement which states that the sum of the squares of the two legs of a right triangle is equal to the square of the hypotenuse.
Output (English): Science