minimum point on a curve

例句：

1. 1. The minimum point on thecurve is where the function reaches its lowestvalue.
   曲线上的最小点是函数达到最低值的地方。
2. 2. The extremum ofthe curve is the point at which thefunction changes direction.
   曲线的极值是函数改变方向的点。
3. 3. Theextremity of thecurve is the point where thefunction crosses the x-axis.
   曲线的极点是函数穿过x轴的点。