Musical instrument classification and some other woodwinds, such as the flute and bagpipe), other wind instruments such as the organ, and the stick-struck santur (a board zither). The distinction between fretted and open was in classic Persian fashion. Musical instrument classification Throughout history, various methods of musical instrument classification have been used. The most commonly used system divides instruments into string instruments, woodwind instruments, brass instruments and percussion instruments; however, other schemes have been devised. The oldest known scheme of classifying instruments is Chinese and dates from the 3rd millennium BC. It grouped instruments according to the materials they are made of. Instruments
Proof that e is irrational Proof that e is irrational The number "e" was introduced by Jacob Bernoulli in 1683. More than half a century later, Euler, who had been a student of Jacob's younger brother Johann, proved that "e" is irrational; that is, that it cannot be expressed as the quotient of two integers. Euler wrote the first proof of the fact that "e" is irrational in 1737 (but the text was only published seven years later). He computed the representation of "e" as a simple continued fraction, which is Since this continued fraction is infinite and every rational number has a terminating continued