Hacker News Reader

Comment by DevX101 | Hacker News Reader

Am I the only one who has to always look up the definition (w/ example image) for concave and convex to differentiate them?

View on HN

I always think that concave goes in, like a cave.

It's probably one of those things people end up memorizing, when learning about lenses or 3d figures like polyhedrons. It's like latitude and longitude. You can try to derive meaning from e.g. "lat = lateral", but then, do the lines go across or are they measuring distance across (which would make the lines vertical)? Either you memorize the correct answer, or you can easily get mixed up by over-analyzing the meaning.

concave -> (cave, cavity) -> hole

convex, you sort of just have to memorize. As best I can tell from introspection, I've associated the sound/visual of "vex" with "outward"

I've been doing a lot of geo-related work lately and confounding latitude and longitude was a regular source of logic errors. Only useful for North America, but my mnemonic for lat/lng is "latitude has a positive attitude". It doesn't necessarily help when identifying which is which on a map, but when using them for calculating proximity or drawing polygons on a map it works every time.

The lines of longitude are always long, whereas the parallels of latitude can be shorter, and are always "parallel" (in some sense).

Vex, as in vertex. Bulging outwards. I think the proper way to remember those (I've struggled with them too) is actually use them a lot. For example, some mathematicians study convex geometry, which is a meaningful subject on its own.

*(lazy ninja edit)

Reply on news.ycombinator.com