shù / xué / kè / shàng / lǎo / shī / jiǎng / jiě / le / děng / zhōu / bù / děng / shì / de / jī / běn / sī / xiǎng

数学课上，老师讲解了等周不等式的基本思想。

In math class, the teacher explained the basic idea of the isoperimetric inequality.