It's like asking you what is the area under a curve on just this line.

这就像问你这条直线上曲线下的面积是多少。

For those of you who haven't, an integral is just the area under a curve.

对于那些没有的人来说，积分就是曲线下的面积。

So the area under a curve can be divided into a set of infinitely tiny rectangles.

所以可以划分弯道下的区域 成一组小矩形。