Art of Problem Solving

Isoperimetric Inequalities: Difference between revisions

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[[Category:Geometry]]
[[Category:Geometry]]
[[Category:Inequality]]
[[Category:Inequalities]]
[[Category:Theorems]]
[[Category:Geometric Inequalities]]

Latest revision as of 16:08, 29 December 2021

Isoperimetric Inequalities are inequalities concerning the area of a figure with a given perimeter. They were worked on extensively by Lagrange.

If a figure in a plane has area $A$ and perimeter $P$ then $\frac{4\pi A}{P^2} \leq 1$. This means that given a perimeter $P$ for a plane figure, the circle has the largest area. Conversely, of all plane figures with area $A$, the circle has the least perimeter.

Note that due to this inequality, it is impossible to have a figure with infinite volume yet finite surface area.

See also