* The [http://en.wikipedia.org/wiki/Circumference circumference] of a [[circle]] is proportional to its [http://en.wikipedia.org/wiki/Diameter diameter], with the constant of proportionality equal to π. | * The [http://en.wikipedia.org/wiki/Circumference circumference] of a [[circle]] is proportional to its [http://en.wikipedia.org/wiki/Diameter diameter], with the constant of proportionality equal to π. |