normal axis

例句：

1. 1. The normal axis of the planet is tilted at an angle to its orbit.
   行星的正常轴倾斜于其轨道。
2. 2. The normal axis of a triangle divides each side into two equal segments.
   三角形的正常轴将每条边分成两个相等的部分。
3. 3. The normal axis of the Earth's gravity field is approximately 9.8meters per second squared.
   地球引力场的正常轴大约以每秒平方九点八米的速度运动。