For any circle, the length of the circumference divided by the length of the diameter is the same, and this number is the value of π. It is equal to 3.14159265 to 8 decimal places. Sometimes π is approximated as . In 1761 Lambert showed, using continued fractions, that π is irrational. In 1882, Lindemann proved further that π is transcendental. π appears in some contexts that seem to have no connection with the definition relating to a circle, as in the Basel problem
and in Wallis’ product
See also tau.