tangent

在几何学中，切线是与圆仅有一个交点的直线。

In geometry, a ___tangent is a straight line that touches a circle at exactly one point.

教授讲课时突然跑题，开始谈论起他最喜欢的足球俱乐部。

The professor went off on a ___tangent during the lecture, talking about his favorite football club instead.

求职面试突然奇怪地跑题，应聘者开始描述他最拿手的野外烹饪食谱。

The job interview took a bizarre ___tangent when the candidate started describing his favorite camping recipes.