The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Education » math-teach

Topic: proper functions?
Replies: 16   Last Post: Dec 28, 2010 1:22 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
kirby urner

Posts: 2,578
Registered: 11/29/05
Re: proper functions?
Posted: Dec 23, 2010 1:03 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On Thu, Dec 23, 2010 at 8:41 AM, Clyde Greeno @.MALEI
<> wrote:
> You ask of a taxonomy of functions ... including a class of what you choose to call "really" functions.
> The latter seems to exclude the constant functions, such as g(x,y)=3  ... as needed for such intersections as 2x+5y=3 ... more precisely, 2x+5y=3sub-(x.y)
> Your class of "really functions" also seems to exclude what Karl Menger called the (First, Second, etc.)  place-selector functions ... as with F(x,y)=x and S(x,y)=y ... on which all of function analysis depends. Apparently, your (postulational) criterion for your "really" functions is that for all  (x,y,...) coordinate-points within the domain of a "really" (numeric-valued) function, the total range of numbers used in any one place always yields more than one value of the function.

Hey cool, someone else who knows about / cites Karl Menger.

Karl contributed this essay to an anthology relating to Einstein's
philosophy (that's what they called it back then), about how we might
want to get off the Euclidean bandwagon some way *other than*
jiggering with the fifth postulate: we could mess with the
definitions. He called his invention a "geometry of lumps" and only
started to derive the ripple effects, leaving it to others to perhaps
build on this proposal.

Enter "claymation station" and other animation applications which
focus on the distribution of light energy through a space. In order
for target energy to register with an observer, it needs to occupy
definite volume ("res extensa" in Descartes vocabulary). In this
sense, all targets are the same in being volumetric, even if some are
more point-like or line-like (or plane-like in the case of surfaces).

Of course this is an idealization in need of further elaboration, and
instead of doing all that work from scratch, I hooked up a neighboring
body of literature that was following just such a course. All the
lumps were topologically tetrahedrons, if anchoring to the family of
volumetric polyhedrons (because the tetrahedron is the simplex or
"first volume" in the world of V,F,E). That brought edges (E), faces
(F) and vertexes (V) into the picture (all at once, ab initio, V + F =
E + 2) which resulted in further articulation and definition through
two volumes of published work, endorsed on the dust jacket by such as
Arthur C. Clarke, early speculator about satellite communications, and
U Thant, a former UN general secretary.

The two tomes in question (by Dick Fuller and on the web for some
years complete with illustrations, thx to Dr. Gray) were also in
collaboration with a retired staff chief and deputy inspector general
under another Dick: Helms (talking about Sonny). These many links to
interesting historical personages opens a lot of windows (and/or
Wikipedia links) for those wishing to explore Americana amidst a
larger body of world literature (Arthur was a resident of Sri Lanka,
while U was Burmese, Sonny lived in Georgetown).

Rather than channel all this through K-12 high school math courses
directly, which would be hopeless, I've been promulgating the above in
a commercial context. That's not to discourage teachers (see below),
but simply to channel around an obviously rickety infrastructure that
doesn't respond to external stimuli very quickly or with much
coordination. The private sector has some faster switches, as do
elements of the public sector. LCDs (flatscreens) bring geometry
directly into the home, as well as geography (the two main subjects we
seek to overlap i.e. res extensa and res cogitans, to get
philosophical about it).

High schoolers visiting one of our coffee shops after school or on
weekends see allusions to these ideas on the LCDs and/or surrounding
poster art and decor (we design in lots of Phi 'n stuff, per Dr.
Livio's influence etc.). They click around on the web and find out
about Karl Menger et al, and start wowing their teachers and friends
with all this esoteric knowledge that actually sounds employable (as
in applicable) to real world problem solving.

> Your question seems to be of whether or not there exists a very simple, classical name for your "really" functions. Probably not. Therefore, you are free to assign to such functions whatever title you choose.  As a word of caution, the word, "real" commonly refers to the "golden" numbers as a continuum. So, -- as opposed to "real functions",  you might wish to consider using an alternative title, such as "fully variable functions" ... meaning variations in each place yields variations in the function values.
> Good query.  Good luck on your efforts to clarify the cognitive structure of the underlying mathematics.
> Cordially,
> Clyde

I'd remind the questioner that you don't need to know the rule for a
function to have a function.

As we all learned in New Math, a function is no more or less than a
set of tuples relating input states to output states. These pairs
should have the property that the same input is never seen with two
different outputs (domain members are monogamous with range members),
however it's fine for any number of input elements to "date" the same

In terms of "correlation", you really don't always know.

That's the game of statistics, to figure out if "x" (e.g. aspartic
acid) is really an influence (e.g. on the "attention span" however
measured). You get a lot of data and search for some rule, perhaps a
linear relationship, though given this is biochemisty, you know
there's a point at which too much of anything is gonna be bad for ya.
Someone might be wanting to test Nutrasweet against Ritalin for
example, perhaps in a bid to get those Pepsi vending machines back in
the schools, dispensing "smart drinks" this time (not my bailiwick,
but I have been following research on Nutrasweet and MSG).

The people working with me on the coffee shops network (I've got chief
officers displayed in the biz logs or chronofile) share readings.
I'll likely point some of them back to this thread.

I'm on the marketing side (CMO) which is what's most active right now,
as coffee shops (some are full bars, but not necessarily those
frequented by high schoolers) won't want to subscribe to the LCD feed
or games if they don't understand what's in it for them (e.g. lots of
high school aged customers geocaching for geometric esoterica, some
kind of "outdoor math" exercise perhaps organized by the math circles
in participating schools, with faculty oversight and approval).


Notes: (re U)
(Dick to Ed)
(he didn't encourage the moniker "Dick" but he was a Richard)
(curriculum developer, US east coaster)
Also see writings by Dr. Loeb and Dr. Istvan Hargittai for more
academic perspectives
(Victoria's intro) (Ed's article at my web site)

> - --------------------------------------------------
> From: "June Lester" <>
> Sent: Wednesday, December 22, 2010 5:30 PM
> To: <>
> Subject: proper functions?

>> Just a quick question for the knowledgeable people of this forum: is there an official term for functions which are "really" functions of their arguments, i.e. their values actually vary with their arguments.  So f(x, y) = x + y is one such, while g(x, y) = x is not.  I tend to say f is a "proper" function of y, but g is not, but I would rather use the official terminology, if there is indeed one.
>> Thanks

Message was edited by: kirby urner

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2017. All Rights Reserved.