他伸出一条手臂，接着又伸出另一条，在两边都接触到了墙，发现巷道很窄；他脚下滑了一下，发现石板很湿。

He extended one arm and then the other, touched the walls on both sides, and perceived that the passage was narrow; he slipped, and thus perceived that the pavement was wet.

youdao

切线是一条直线，刚好接触到曲线，所以跑切线是从一个弯道跑到另一个最短的距离。

A tangent is a straight line that just touches a curve, so the concept of "running the tangents" is to run the shortest distance possible by running straight from one curve to the next.

youdao

当你使这两条导线一接触，这台机器就会立刻开始运转。

When you contact these two wires, the machine will start at once.

youdao