rotation center的用法和樣例：
例句
- It is defined as the perpendicular distance between the follower's axis of motion and the center of the cam.
從凸輪的轉動中心到直動推桿的導路之間的垂直距離。 - But some caution is needed in choosing the center of rotation to be employed in evaluating the torques and calculating the motion.
但是，在選擇用來求力矩和計算運動的轉動中心時，需要注意幾個問題。
