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Possible Duplicate:
Why does “convex function” mean “concave up”?

Forty years ago I recall seeing the definition of a convex function (ie, that the points on the line segment joining two points on its graph are above its graph), with the definition of a concave function being that its negative is convex. Now, teaching high school mathematics, I am seeing “concave up” used with the meaning of “convex”, and “concave down” to mean “concave”. I can sympathize with the strong intuitive basis of this high school terminology, but I was just wondering whether is goes beyond high school. For example, when you are “really” doing mathematics, you speak of, say, the concavity of the logarithm, right?, never its “concave-down-ness”, right?

added just before posting: I see that T.. has pretty much answered this already here on MSE at a related post. Here’s the link:

Why does "convex function" mean "concave *up*"?

If you all want to close this question of mine as a duplicate, I won’t mind.

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    I don't mind the question being closed, but I do not think it is accurate to call it an exact duplicate. The other question was only asking for help in understanding the terminology, whereas I was questioning the propriety of the terminology:)2011-09-29

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