Complex analysis, traditionally known as the theory of functions of a complex variable, is the branch of mathematical analysis that investigates functions of complex numbers. It is useful in many branches of mathematics, including algebraic geometry, number theory, applied mathematics; as well as in physics, including hydrodynamics, thermodynamics, mechanical engineering and electrical engineering.
Murray R. Spiegel described complex analysis as "one of the most beautiful as well as useful branches of Mathematics".
This page is about the history of approximations for the mathematical constant pi (π). There is a table summarizing the πchronology of computation of . See also the πhistory of for other aspects of the evolution of our knowledge about mathematical properties of π.