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 a proof that "e" is not a root of a second degree polynomial with rational coefficients. This last fact implies that "e" is irrational. His proofs are similar to Fourier's proof of the irrationality of "e". In 1891, Hurwitz explained how it is possible to prove along the same line of ideas that "e" is not a root of a third degree polynomial with rational coefficients. In particular, "e" is irrational. More generally, "e" is irrational for any non-zero rational "q". Proof that e is irrational The number "e" was introduced by Jacob Bernoulli in 1683. More than half a