Changes

| url = http://turnbull.mcs.st-and.ac.uk/~history/Biographies/Lambert.html

| url = http://turnbull.mcs.st-and.ac.uk/~history/Biographies/Lambert.html

| title = Biography of Johann Heinrich Lambert

| title = Biography of Johann Heinrich Lambert

| accessdate = 2012-02-12}}</ref> proved this in 1761 by showing that '''π''' is an [[irrational number]]; Lindeman<ref>{{cite web

| accessdate = 2012-02-12}}</ref> proved this in 1761 by showing that '''π''' is an [[irrational number]], which means that it can't be expressed as a fraction; Lindeman<ref>{{cite web

| url = http://turnbull.mcs.st-and.ac.uk/~history/Biographies/Lindemann.html

| url = http://turnbull.mcs.st-and.ac.uk/~history/Biographies/Lindemann.html

| title = Biography of Carl Louis Ferdinand von Lindemann

| title = Biography of Carl Louis Ferdinand von Lindemann

| accessdate = 2012-02-12}}</ref> went further in 1882 and proved that '''π''' is a [[transcendental number]] which means it can't be expressed as the solution to any simple equation).

| accessdate = 2012-02-12}}</ref> went further in 1882 and proved that '''π''' is a [[transcendental number]] which means that it can't be expressed as the solution to any simple equation).

The approximate value quoted above is accurate enough to calculate the circumference of a circle of the size of the Earth with an error of only about 1 millimetre. For rough approximations, the fraction 22/7 (= 3.142857...), correct to 2 decimal places, is sometimes used.  A more accurate fractional approximation is 355 / 113 (= 3.14159292...), which is correct to 6 decimal places.

The approximate value quoted above is accurate enough to calculate the circumference of a circle of the size of the Earth with an error of only about 1 millimetre. For rough approximations, the fraction 22/7 (= 3.142857...), correct to 2 decimal places, is sometimes used.  A more accurate fractional approximation is 355 / 113 (= 3.14159292...), which is correct to 6 decimal places.