a differential gear的用法和样例：
- A : Yaw is controlled through a differential gear within the transmission.
- In the wide weaving machine, the difference of warp tension on two beams are reduced by using a differential gear train of let-off motion double beams (side by side).
- A zero may also be called a differentiator.
- Rewinding shaft complete with machinery differential gear device, tension can be balanced.
- Newton's second law can be expressed as a differential equation.