Calculus help

Mostess · Post by **Mostess** » Thu May 05, 2005 8:03 am

I need some calculus help: I have a third-order curve and I'm trying to find the exact "bend points" but my limited calc knowledge isn't helping. PM me if this sounds like fun to you.

Adam! · Post by **Adam!** » Thu May 05, 2005 10:42 am

Solved

Mostess · Post by **Mostess** » Thu May 05, 2005 10:53 am

You may all continue with your normal lives now. Thank you for your attention.

bz£ · Post by **bz£** » Thu May 05, 2005 11:01 am

Mostess wrote:You may all continue with your normal lives now.

Because if you're willing to drop everything to work on advanced maths then you clearly have a normal life going on.

Leaf · Post by **Leaf** » Thu May 05, 2005 11:56 am

ah damn... did I miss this one?

Mathfight.com

sweet. A home page for Puce!!!

Dan-O from Five-O · Post by **Dan-O from Five-O** » Thu May 05, 2005 4:23 pm

Puce, do you work on taxes as well?

What am I talking about, that's math no one can figure out.

Post by jb » Thu May 05, 2005 7:20 pm

Leaf wrote:ah damn... did I miss this one?

Mathfight.com

sweet. A home page for Puce!!!

A problem is presented each week. People come up with proofs/solutions and submit them. Visitors vote for their favorite, and the winner wins.

Somebody do it, it would be neat. I can barely add, myself, so I'd be a terrible FightMaster for Math Fight.

erik · Post by **erik** » Thu May 05, 2005 7:27 pm

Man, this was like the best math class I ever took in college. The teacher would present a problem set on Monday, and have them due the next Monday. People would come up with these <i>sick</i> ways of proving stuff, that would just blow your mind that someone would even think of approaching the problem that way. She'd be all "Any solve this differently?" and then someone gets up to the chalkboard and does some weird ass stuff and freaks you the hell out.

sparks · Post by **sparks** » Thu May 05, 2005 9:31 pm

No, skip the proofs. The entires would just be answers.

Answer....................Votes Received

"4"..........................5
"4"..........................16
"4"..........................1
"pants ha ha ha".......48
"5"..........................2
"4"..........................5

Adam! · Post by **Adam!** » Thu May 05, 2005 9:47 pm

sparks wrote:"pants ha ha ha".......48

No freaking kidding. "Pants ha ha ha" would get my vote every time.

HeuristicsInc · Post by **HeuristicsInc** » Fri May 06, 2005 7:40 am

that was hilarious. "pants ha ha ha"
-bill

Post by jb » Fri May 06, 2005 10:05 am

erikb wrote:Man, this was like the best math class I ever took in college. The teacher would present a problem set on Monday, and have them due the next Monday. People would come up with these <i>sick</i> ways of proving stuff, that would just blow your mind that someone would even think of approaching the problem that way. She'd be all "Any solve this differently?" and then someone gets up to the chalkboard and does some weird ass stuff and freaks you the hell out.

Yeah, that's what I think would be fascinating. Different ways to come to the same conclusion, some more elegant than others. Kind of Song Fightey.

LMNOP · Post by **LMNOP** » Fri May 06, 2005 11:23 am

Okay. Practice run. And you don’t have to be a math genius.

To see if a number is a multiple of 7, take off the last digit, double it, and subtract it from what’s left. If your answer is a multiple of 7, so is your original number.

Examples:
385: 38 – (2 x 5) = 28 which is a multiple of 7 therefore so is 385.
386: 38 – (2 x 6) = 26 which is not a multiple of 7 therefore neither is 386.
1,771: 177 – (2 x 1) = 175; 17 – (2 x 5) = 7 therefore 1,771 is a multiple of 7.

Yes, you could more easily just do the division in your head but I’ve always loved this test because it seems so counter-intuitive.

So prove it. Elegantly.

erik · Post by **erik** » Fri May 06, 2005 2:25 pm

LMNOP wrote:To see if a number is a multiple of 7, take off the last digit, double it, and subtract it from what’s left. If your answer is a multiple of 7, so is your original number.

Examples:
385: 38 – (2 x 5) = 28 which is a multiple of 7 therefore so is 385.
386: 38 – (2 x 6) = 26 which is not a multiple of 7 therefore neither is 386.
1,771: 177 – (2 x 1) = 175; 17 – (2 x 5) = 7 therefore 1,771 is a multiple of 7.

The original number takes the form 10x + y (where x and y are whole numbers), and if it's a multiple of 7 then we can say that 10x + y = 7 * SOMETHING, let's say 10x + y = 7a (where a is a whole number). The "proof number" takes the form x - 2y, and if it's a multiple of 7 then we can say that x - 2y = 7 * SOMETHING ELSE, so lets say x - 2y = 7b (where b is a whole number). If we can change the second equation into the first, then that will prove that showing that the second form is a multiple of 7 necessitates the first form being a multiple of seven.

x - 2y = 7b . . . . . . (mutliply both sides by 10)

10(x - 2y) = 70b . . . . . . (reorganize both sides)

10x -20y = 7(10b) . . . . . . . (add 21y to both sides)

10x + y = 7(10b) - 21y . . . . . . . .(reorganize right side)

10x + y = 7(10b - 3y)

If the "proof number" is divisible by 7 (equal to 7 times SOME WHOLE NUMBER), then the original number must be divisible by 7 (equal to 7 times SOME OTHER WHOLE NUMBER).

pants ha ha ha

j$ · Post by j$ » Fri May 06, 2005 5:26 pm

Oh sweet jesus .....

sparks · Post by **sparks** » Fri May 06, 2005 7:04 pm

I'm desperately looking for that Nevada picture now. This thread must die before the idea goes any further.

LMNOP · Post by **LMNOP** » Fri May 06, 2005 8:36 pm

Ah, well done -- I think that's about as clear as it can be presented. You even got the "pants" part which was part of my planned smart-ass response to the first posted solution.

Dan-O from Five-O · Post by **Dan-O from Five-O** » Fri May 06, 2005 9:04 pm

I once had my name done as a math problem. It went like this:

Southwest_Statistic wrote:
the Jazz wrote:How are you guys dealing with the hyphen character? Looks like a pair of ranges in base 32 to me (aka Duotrigesimal). Translated into base 10 we have the range 13,655 - 24 subtracted from the range 510,944-24. Which, assuming these ranges are inclusive, could produce the range 510,944 - 13,656, which would mean that:
Code: Select all
  five-o
-  dan-o
----------
  five-dao
Dan-O from Five-O

No no no... you guys are all wrong. He was merely encoding a hidden meaning into his name using IBM standard ASCII character codes. I can't believe no one else sees this. Look:
Code: Select all
"Dan" = 68 + 97 + 110 = (275)

"-O" = 45 + 79 = (124)

"from" = 102 + 114 + 111 + 109 = (436)

"Five" = 70 + 105 + 118 + 101 = (394)

"-O" = 45 + 79 = (124)

...therefore...

275 + 124 + 436 + 394 + 124 = (1353)
After thinking about the above fact all day long, I really honestly could not for the life of me figure out what the significance of "One-Thousand-Three-Hundred-Fifty-Three" could possibly be.

Then it hit me! The little light bulb inside my head clicked on and I realized that he wasn't encoding the "-" character! He was using in it's mathematic form as a modifier in conjunction with the IBM-ASCII significance of the "O" character, the value of which is "79". Therefore:
Code: Select all
"Dan-O" = [275] - 79 = (196)

"from" = [436] = (436)

"Five-O" = [394] - 79 = (315)

...and so...

196 + 436 + 315 = 947
947! Of course! Why didn't I see it before! 947 (as everyone knows) is the new overlay area code in Michigan that will be replacing the 248 geographic area, as they have exhausted all the 248 numbers. This includes "Clarkston Michigan", where I live and have lived for the last 5 years.

http://www.whitepages.com/9900/maps/DET

Obviously, this is an omen of some kind. Any theorys?

I'm looking for alternative theories if you folks want to give it try.

Dan-O from Five-O · Post by **Dan-O from Five-O** » Wed May 11, 2005 8:55 pm

I wish we had stats for how many threads I've killed. I know I would be at least a 50% shooter.

Damn it's nice for a married guy to get the last word in once in a while.