Numbers have been known in some form for nearly 4,000 years

Historians aren't sure when or how this number was first discovered,but it's been known in some form for almost 4,000 years.Estimates of it appear in the works of ancient Greek,Babylonian,Chinese,and Indian mathematicians.And it's even believed to have been used in building the Egyptian pyramids.Mathematicians estimated it by inscribing polygons in circles.