The Lumber Room

"Consign them to dust and damp by way of preserving them"

Convex and concave

with 7 comments

A mnemonic for ‘convex’ and ‘concave’:


A convex function


A conCAVE function

Two mnemonics are better than one.

Written by S

Tue, 2009-03-17 at 15:56:28

Posted in Uncategorized

Tagged with ,

7 Responses

Subscribe to comments with RSS.

  1. Oh yeah? I guarantee that at least one student will remember it like this and get it exactly wrong:

    concaVe (with a big V)

    Convex (with a big C)


    Tue, 2009-03-17 at 16:10:45

    • Heh, personal mnemonics often have that problem. :)

      I associate “convex” and not “concave” with the “v” sound (it’s the first letter where they’re different, so the words are really “vex” and “cave”), so it works for me. If I thought of the “big C”, I would probably reason that it the “c” can go with either word, and “concave” has a better claim on it.

      I see your point, though… one should always devise one’s own mnemonics; others’ will only confuse.


      Tue, 2009-03-17 at 16:16:56

  2. In the chapter named “Los Alamos from Below” in Surely You’re Joking…, Feynman describes what the view was like “from the bottom”, his metaphor for working as hands-on as he could, having immersed himself entirely in his work.

    I read this book at the same time I had a real analysis course in college, and owing to some illogical association-by-simultaneity conflation, I came to differentiate convex and concave functions by “viewing from the bottom” (i.e. literally). Never had trouble with the definitions since.

    To each his own, I guess. Mnemonics are funny constructs.


    Tue, 2009-03-17 at 18:26:17

    • Ah right, that would work too. These days I seldom encounter “convex” and “concave” in their natural-world meanings; it is usually in a mathematical context. So I didn’t even understand your mnemonic at first; maybe some day I’ll need a mnemonic for remembering which means ‘bulging outward / toward you’ and which means the other. :)


      Wed, 2009-03-18 at 00:36:05

  3. […] convex function (need a mnemonic?) is such that for any λ in […]

  4. I’m a 3D modeler so I have to model convex surfaces all the time for proper collision detection, so the terms tend to stick without the need for a mnemonic. Back when I was first learning though, I just thought a cave is a hole in a mountain which goes inward and that makes concave easy to remember. This only leaves convex which means it would go outwards.


    Mon, 2018-07-02 at 13:12:40

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: