Changes

:<big><math>Area= \pi r^{2}</math></big>

:<big><math>Area= \pi r^{2}</math></big>

The value of pi is approximately 3.14 or 22/7. The exact value cannot be expressed as a fraction or as a decimal number, regardless of how many digits are used.<ref>{{cite web

The value of pi is approximately 3.14 or 22/7. The exact value cannot be expressed as a fraction or as a decimal number, regardless of how many digits are used. Lambert proved this in 1761 by showing that pi is an [[irrational number]], which means that it can't be expressed as a fraction.<ref>{{cite web

| 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