What is the square root of 2?
The square root of 2 is about 1.41421356. It is the number that, when multiplied by itself, gives 2, and it is irrational, so its decimals never end or repeat.
The square root of 2 is the length of the diagonal of a square whose sides are 1 unit long, according to the Pythagorean theorem. It appears often in geometry, engineering and design.
It is believed to be the first number proven to be irrational, meaning it cannot be written as a fraction of two whole numbers. According to legend, the discovery shocked the followers of the Greek philosopher Pythagoras, who believed all numbers were ratios.
Paper sizes
International paper sizes, such as A4, use the square root of 2. The ratio of the long side to the short side is about 1.414, so when you fold an A4 sheet in half, you get an A5 sheet with the same proportions.
Did You Know?
A Babylonian clay tablet called YBC 7289, about 3,800 years old, shows the square root of 2 calculated to about six decimal places.