Shù / xué / kè / shàng / lǎo / shī / yòng / xuán / zhuǎn / zhǐ / biāo / shuō / míng / qū / xiàn / rào / diǎn / xuán / zhuǎn / de / cì / shù

数学课上，老师用旋转指标说明曲线绕点旋转的次数。

In math class, the teacher used the winding number to show how many times a curve rotates around a point.