WTF is up with the backwards 6 in math!?!?!?

[DcifrThs]

for years ive lived perfectly content in using the "d" in fairly simple PDEs like:

dS=uSdt +sSdWt (well i didn't know that one years ago but you know what i mean)

and using the backwards 6 in more complex (2nd order) ones (i'll use a 6 here for the backwards 6) like:

dP=-(6C/6S*uS+6C/6S +1/2*6^2C/6S^2)dt ...

well i was doing my homework and i found myself writing:

dP=-(6C/dS*uS+6C/dS + 1/26^2C/dS^2*s*S)dt...

so wtf is the point of having a backward 6 if using a d means (as far as i can tell) the same darned thing??

its just like using weird symbols where way simpler ones will do. they both seem to mean looking at the variables concerned over infinitesimal changes of another variable or parameter. time in one case and stock price in another...

i mean, the dt is always intact at the end so wtfs the difference if i use the d in dS, talking about small changes in an asset price, like the d in dt, talking about small changes in time??

-Barron

[protoverus]

Are you referring to the lowercase greek letter delta?

[DcifrThs]

[ QUOTE ]
Are you referring to the lowercase greek letter delta?

[/ QUOTE ]

it all stands for the same thing. small, infinitesimal changes. unless your'e using delta to stand for a function on its own.

Barron

[DoomSlice]

I believe it is used to mean partial derivative, while the d is used as the explicit "change in".

[_TKO_]

[ QUOTE ]
it is used to mean partial derivative

[/ QUOTE ]

[tyrus72]

You get the award for Best Unintentional Comedy in a Post.

Once you figure out the "backwards 6", then can try to explain that silly "end table" thingy used in the equation for a circle's circumference.

[daryn]

R U SIRIUS?

[daryn]

[ QUOTE ]
You get the award for Best Unintentional Comedy in a Post.

Once you figure out the "backwards 6", then can try to explain that silly "end table" thingy used in the equation for a circle's circumference.

[/ QUOTE ]

you mean stonehenge?

[gumpzilla]

I assume this has already been answered, but I'll throw in my two cents.

The "backwards 6" is used to indicate that you're taking a partial rather than a total derivative. There are times where this distinction is important. Suppose you have a function H that depends on three variables: p, q and t. Further suppose that p and q are functions of t. Then you can talk about the partial "backwards 6" derivative of H with respect to t, which is just the obvious one. You can also talk about the total derivative dH/dt, which requires that you use the chain rule.

[SmileyEH]

Economists....pfffffft.

-SmileyEH

[DcifrThs]

[ QUOTE ]
R U SIRIUS?

[/ QUOTE ]

the title was intentionally funny. the question remains, whem im feeling lazy, why can't i simply write "6X/dY". i know im not dividing by the first derivative of Y. there's nothing else it could be other than a partial and have the equation make sense. in these cases i just wrote it b/c i hate the stupid backwards 6.

so wtf is up w/ that shiiiit.

-Barron

[_TKO_]

[ QUOTE ]
i know im not dividing by the first derivative of Y. there's nothing else it could be other than a partial and have the equation make sense.

[/ QUOTE ]

The division symbol is not division; it means "with respect to". As for the equation making sense, not everyone knows what you mean.

[PokerPadawan]

.......

this post made me dumber.

[soko]

[ QUOTE ]
.......

this post made me dumber.

[/ QUOTE ]

if you take your post out of context it becomes even more funny

[morphball]

I always used the triangle (or bigger case delta) for representing "change in" something...

[Nut4Dawgs]

PDE = Partial Differential Equation? (Mathematics?)

If you're using your computer, I thought the "Greek Math Symbol" font set had all the symbols you're referring to. (There's also an open source app, "Sprankle Character Map.")

If you're using pen/pencil and paper, why is this a problem?

/images/graemlins/confused.gif

[DcifrThs]

[ QUOTE ]
PDE = Partial Differential Equation? (Mathematics?)

[/ QUOTE ]

yup.

[ QUOTE ]


If you're using your computer, I thought the "Greek Math Symbol" font set had all the symbols you're referring to. (There's also an open source app, "Sprankle Character Map.")

[/ QUOTE ]

word has the greek symbol thingy? is it in the normal font section?

[ QUOTE ]

If you're using pen/pencil and paper, why is this a problem?

/images/graemlins/confused.gif

[/ QUOTE ]

i was writing an email with the above. thats what irked me and i started just writing 6C/dS...

Barron

[Nut4Dawgs]

[ QUOTE ]

word has the greek symbol thingy? is it in the normal font section?

[/ QUOTE ]
If you're using MS Word, you've probably got the font. MS includes it in Windows OpSys. Look in the Accessories/Systems Tools for Character Map. Open it and type in "G." Then drop down the menu and look for Greek Math Symbols. They're all there.

If, for some reason, you don't have the font, PM me your e-maill address and I'll send it to you. It's a small file.

[ZeeJustin]

[ QUOTE ]
[ QUOTE ]
You get the award for Best Unintentional Comedy in a Post.

Once you figure out the "backwards 6", then can try to explain that silly "end table" thingy used in the equation for a circle's circumference.

[/ QUOTE ]

you mean stonehenge?

[/ QUOTE ]

Clearly he means Pie. Mmmmmmm... Pie.

[PokerPadawan]

[ QUOTE ]
Clearly he means Pie. Mmmmmmm... Pie.

[/ QUOTE ]

http://www.weebl.jolt.co.uk/pie.htm

[Nut4Dawgs]

British humour is, frequently, an acquired taste.

[atrifix]

I'm not sure what font you're referring to here, since I have no greek font. I do have all the extended characters in normal fonts (Times, Courier, etc.) though. I prefer to use Symbol, though, because extended characters sometimes display very weirdly.

On a completely unrelated topic, if anyone knows of a font with a v-bar (v with a bar over it), let me know.

[Nut4Dawgs]

I'm not referring to the Greek/ Cyrillic font.

http://i11.photobucket.com/albums/a200/Nut4Dawgs/Thread%20Pics/characmap.jpg

[ QUOTE ]
...because extended characters sometimes display very weirdly.

[/ QUOTE ]
When this happens it's because the font you've used is not on the viewer's system.

[ QUOTE ]
...if anyone knows of a font with a v-bar (v with a bar over it), let me know.


[/ QUOTE ]
Do you mean the upside down Delta? Look at the lower right of the pic.

[DcifrThs]

[ QUOTE ]
I'm not referring to the Greek/ Cyrillic font.

http://i11.photobucket.com/albums/a200/Nut4Dawgs/Thread%20Pics/characmap.jpg

[ QUOTE ]
...because extended characters sometimes display very weirdly.

[/ QUOTE ]
When this happens it's because the font you've used is not on the viewer's system.

[ QUOTE ]
...if anyone knows of a font with a v-bar (v with a bar over it), let me know.


[/ QUOTE ]
Do you mean the upside down Delta? Look at the lower right of the pic.

[/ QUOTE ]

when i go to word--> format-->font, i only see the "Symbol" font there and i dont see a key for what letter produces what symbol.

Barron

[Nut4Dawgs]

If you don't want to memorize all the keystroke combinations, the simplest thing to do is:

Open the Character Map (CM). Set it to Greek Math Symbols (GMS). Move the window off to one side of your screen.

Open your Word .doc and reduce the width of the window so you can see the CM. When you want to insert a character, "drag and drop" it. Suggestion: Since pasting the symbol will now set the font in your .doc to GMS, add an extra space and paste behind it. Try it, you'll see what I mean.

The Character Code referred to at the bottom left of the CM is the Unicode equivalent. Much more complicated, IMO. NUM LOCK+ALT+xxxx. And you have to know/remember all the damned combinations. (Luv that Drag'n'Drop thingie!)

[atrifix]

Symbol is rather easy, I believe a = alpha, b = beta, etc. Or you could cut/paste.

[atrifix]

[ QUOTE ]
I'm not referring to the Greek/ Cyrillic font.

[/ QUOTE ]
Interesting--I hadn't seen the font you were referring to, but I downloaded it. I think it comes with Corel. Personally, I use the Mathematica fonts, but maybe this will enable me to not switch fonts.

[ QUOTE ]
Do you mean the upside down Delta? Look at the lower right of the pic.

[/ QUOTE ]That's close, but not really what I had in mind...I really meant a v-bar. Scientists may claim that it represents average velocity or the tail volume ratio, but we all know it really just assigns truth-values. The other thing I am looking for is turnstiles with slashes through them (like http://www.w3.org/TR/MathML2/glyphs/022/U022AD.png), but I imagine that I will have to use latex or something for that.

[Mik1w]

[ QUOTE ]
[ QUOTE ]
R U SIRIUS?

[/ QUOTE ]

the title was intentionally funny. the question remains, whem im feeling lazy, why can't i simply write "6X/dY". i know im not dividing by the first derivative of Y. there's nothing else it could be other than a partial and have the equation make sense. in these cases i just wrote it b/c i hate the stupid backwards 6.

so wtf is up w/ that shiiiit.

-Barron

[/ QUOTE ]

could it not be just dx/dy?

dx/dy is when all other symbols are constants,
6x/6y is when they are not but are treated as if they are.

in terms of the differrntiating process I dont think it matters, but its conventional to use this notation, because otherwise you'd get things that really don't make sense

[MonsterJ]

It is true what they say about MBA students.