zài / píng miàn jǐ hé / zhōng / děng zhōu bù děng shì / shuō míng / zài / zhōu cháng / xiāng tóng / de / qíng kuàng / xià / yuán / de / miàn jī / zuì dà

在平面几何中，等周不等式说明，在周长相同的情况下，圆的面积最大。

In plane geometry, the isoperimetric inequality states that among figures with the same perimeter, a circle has the greatest area.