How to Find Phi

Egypt has found phi about at 200 BC and the value for phi is 3.16. They get that value from the formula of circles area that is square of open bracket diameter times eight over nine close bracket. We know that diameter or d equals two times radius (r), so we get the formula of circles area is open bracket eight over nine in bracket times two of r close bracket square equals sixty four over eighty one in bracket times four of r square equals three point one six times r square. Long time after that Archimedes at 250 BC using phi, but with a different value that is three point one four like which we use now.