About PiNumpad. The Square Root Of 2

PiNumpad is a free memory trainer for the square root of 2 (1.41421356237309...), the square root of 2, the first known irrational number. This page is the practice mode: the numpad path is hidden and you tap the square root of 2 digits entirely from memory. Your score is saved locally between sessions.

Practice from memory. In play mode, the numpad path is hidden. You must tap each digit of the sequence from memory alone, with no visual guide. A correct tap advances the path; an incorrect tap triggers a brief error sound and a shake. Your score, the number of digits or primes you can enter without error, is stored locally so you can track progress across sessions.

The irrationality of √2 was proved by the ancient Greeks, legend has it that the discovery so disturbed the Pythagoreans that they drowned the mathematician who found it. It appears in geometry, signal processing, and the diagonal of any unit square. Tap the digits on the on-screen numpad in the correct sequence. Use Study mode first to learn the path, then switch to Play to test retention. Hold the hint button to reveal the path briefly if you are stuck.

PiNumpad is designed for geometry students, engineers, computer scientists, and anyone interested in the history of mathematics and irrational numbers. It runs entirely in the browser with no account, no installation, and no cost. Progress is saved locally using your browser's storage.

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