The logarithm with the base of n is recorded as. Logarithmic symbol log is derived from Latin logarithm and was first used by Italian mathematician cavalieri. At the beginning of the 20th century, the modern representation of logarithm was formed. For the convenience of use, people gradually recorded the ordinary logarithm with the base of 10 and the natural logarithm with the base of irrational number e as lgN and lnN respectively.