1. Because there is no abrasion between the concave and convex, the nut is reusable. 由于凹面与凸面之间没有磨损，螺母可以重复使用。
2. A small curve in the sliding part of the convex top of the lower nut acts as the wedge. 下螺母凸顶的滑动零件上有一条小弧线充当楔块。
3. It is locally convex in the sense that it has no loops and the curvature never changes sign. 它的局部是凸的，因为它没有环路，且曲率永远不会改变符号。
4. You will then be making circles around the other car, but when seeing from above, both of you are driving forward all the time and your path will be convex. 然后你将会一直绕另一辆车转，但当你从上面看，你们两个一直在向前行驶且你们的路径是凸形的。
5. They're lenses because they're convex vessels, and when they're full of water, they act as a lens and you see the horizon in them, upside down and backwards. 它们是透镜，因为它们是凸面容器，当它们盛满水后，它们可作为透镜使用，你可以看到它们里面上下颠倒的地平线。
