## Search found 221 matches

- Mon Nov 01, 2010 4:19 am UTC
- Forum: Mathematics
- Topic: My idea on why math is hard...
- Replies:
**28** - Views:
**4003**

### Re: My idea on why math is hard...

There's a nice quote (which I'll misquote here and not attribute since I can't remember his name) by a Mathematician that talked about Math being impossibly hard while you try to learn it, and then after you 'see the light' and figure out that problem/idea/proof it becomes so trivially easy that you...

- Wed Sep 29, 2010 4:59 pm UTC
- Forum: Mathematics
- Topic: Ideas for a "Quadratic Equation" class demonstration/game?
- Replies:
**13** - Views:
**7211**

### Re: Ideas for a "Quadratic Equation" class demonstration/gam

One would think that if they already knew the equation they would have already done the derivation.

Kirby wrote:If they already know the equation, then you could derive it for them by completing the square.

- Mon Sep 13, 2010 5:08 am UTC
- Forum: Mathematics
- Topic: Which is it? (straight line or circle through a portal?)
- Replies:
**33** - Views:
**5035**

### Re: Which is it?

antonfire wrote:It's a straight circle.

Maybe it's bi, with hetero-circular leanings.

- Tue May 11, 2010 6:02 am UTC
- Forum: Mathematics
- Topic: Taylor Series
- Replies:
**15** - Views:
**3231**

### Re: Taylor Series

Taylor series can be thought of as a method to determine what the power series for a function is. the 1/(1-x) trick is great when it works quickly and easily... but that's not always the case. So let me get this straight: the Taylor Series is NOT a series in and of itself, but a method of FINDING a...

- Mon May 10, 2010 5:04 am UTC
- Forum: Mathematics
- Topic: Taylor Series
- Replies:
**15** - Views:
**3231**

### Re: Taylor Series

Taylor series can be thought of as a method to determine what the power series for a function is. the 1/(1-x) trick is great when it works quickly and easily... but that's not always the case. With taylor series we start off by assuming that a function does have a power series representation (center...

- Wed Apr 21, 2010 5:56 am UTC
- Forum: Mathematics
- Topic: Wanted: punch line for joke
- Replies:
**15** - Views:
**3566**

### Re: Wanted: punch line for joke

avoiding the math punchlines I'll just go with the:

Are we talking 12 oz soda or those wimpy 8oz cans?

Are we talking 12 oz soda or those wimpy 8oz cans?

- Mon Mar 08, 2010 7:19 am UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**493571**

### Re: What's the derivative of x?

BlackSails wrote:Why is it 0? X could very easily be a function of y.

For example, [imath]x=f(y)[/imath] where [imath]f(\cdot)[/imath]is the "append \ to the argument" function.

Other fun uses of this function are [imath]f(P)=R, f(O)=[/imath]Q, and [imath]f(|\,|)=[/imath]N.

**Spoiler:**

- Wed Dec 09, 2009 8:34 am UTC
- Forum: Mathematics
- Topic: Wrong on the Internet: John Gabriel
- Replies:
**185** - Views:
**66753**

### Re: Wrong on the Internet: John Gabriel

I keep going back to his knol... I don't know why, maybe I feel sorry for the guy. I keep wondering if he's inflating his own ratings on the page or if he's really convincing some people that he knows what he's talking about. I hope it's him; I don't want to think about his writing misleading people...

- Wed Nov 18, 2009 9:43 pm UTC
- Forum: Mathematics
- Topic: Fundamental Theorem of Calculus
- Replies:
**16** - Views:
**2560**

### Re: Fundamental Theorem of Calculus

It's refreshing to have people want to know why a theorem works, especially when you want it enough to go and research it a bit and to ask others for some help. In the School where I've taught Calc I I've only had a very small handful of students who felt this way, most seem to just want the bare mi...

- Fri Nov 06, 2009 9:09 pm UTC
- Forum: Mathematics
- Topic: What aspect of a fn causes integration by parts to fail
- Replies:
**16** - Views:
**2575**

### Re: What aspect of a fn causes integration by parts to fail

the classic \int e^x \sin(x) \, dx class of problems where you do some integration by parts (twice) and get back the original integral, do some algebra and solve for the integral A simpler (less error-prone) approach would be to differentiate it twice. I'll admit that I don't know that tric...

- Fri Nov 06, 2009 8:29 am UTC
- Forum: Mathematics
- Topic: What aspect of a fn causes integration by parts to fail
- Replies:
**16** - Views:
**2575**

### Re: What aspect of a fn causes integration by parts to fail

Here is an "analogous" problem using only algebra. Let's solve for x! I'll start off with just an x . Of course we may write x=x . Now I'll add and subtract the same thing to the right hand side: x=x+1-1 . I'll subtract x from both sides and get 0=1-1 . Just as when you did integration by ...

- Mon Sep 28, 2009 6:01 am UTC
- Forum: Mathematics
- Topic: Limits with square roots
- Replies:
**6** - Views:
**2262**

### Re: Limits with square roots

(mr-mitch beet me to the punch!) Notice that what you did with the log's was unnecessary. In your first step you moved the half power out of the log, then did some more steps including the "key step" of getting that "divide numerator and denominator by x" involved, and finaly put...

- Thu Sep 10, 2009 6:55 am UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**493571**

### Re: Favorite math jokes

Monika wrote:HINT: Use l'Hôpital's rule , multiple times if necessary.

I would argue that this is the math equivalent of a pun.

::groan::

And I would argue that it's just a bad hint.

- Thu May 28, 2009 10:16 pm UTC
- Forum: Mathematics
- Topic: Integrals trig substituation
- Replies:
**4** - Views:
**740**

### Re: Integrals trig substituation

For the limits, usually I drop the limits while doing the substitution then at the end substitute x back in and use the original limits. A number of students fall into a "bad habit" of doing this AND connecting each of their steps with "equal signs". That is they start out doing...

- Wed May 20, 2009 2:16 am UTC
- Forum: Mathematics
- Topic: Calculus: Integration problem
- Replies:
**25** - Views:
**2191**

### Re: Calculus: Integration problem

How is remembering the derivative of arctan more fundamental? Trig substitution can derive such derivatives. My use of the word fundamental assumes that the curriculum was learned in a certain order. Assuming one learns derivatives before integrals, assuming one learns forward substitutions before ...

- Tue May 19, 2009 5:36 pm UTC
- Forum: Mathematics
- Topic: Calculus: Integration problem
- Replies:
**25** - Views:
**2191**

### Re: Calculus: Integration problem

this is not a trig substitution problem. x = \sqrt{3} \tan \theta + 2 . Perhaps a more accurate statement would be there is a more fundamental tool to evaluate this integral, namely recalling the derivative of arctan and using a "u-substitution". However for the majority of students (at l...

- Sat May 02, 2009 6:16 am UTC
- Forum: Mathematics
- Topic: Help with a Math Problem
- Replies:
**11** - Views:
**1756**

### Re: Help with a Math Problem

NathanielJ wrote:I'm a little surprised that the name "Samuel" was still available on these forums. Neat.

Best answer yet.

- Fri May 01, 2009 7:10 pm UTC
- Forum: Mathematics
- Topic: A polynomial problem
- Replies:
**2** - Views:
**680**

- Fri May 01, 2009 7:08 pm UTC
- Forum: Mathematics
- Topic: Help with a Math Problem
- Replies:
**11** - Views:
**1756**

### Re: Help with a Math Problem

Taly and Marc open a Registered Home Ownership Savigs Plan that pays 6% iterest compouded semi-annually. For 4 years, they invest $500 every 5 months in the plan. Determine the amount of interest they earn. Solution may be found by reading your text book and finding the appropriate formula to plug ...

- Mon Apr 27, 2009 9:05 pm UTC
- Forum: Mathematics
- Topic: Any significance to this fact Re: FLT
- Replies:
**5** - Views:
**938**

### Re: Any significance to this fact Re: FLT

I was all set to read something about faster than light travel and then I get Fermat instead. Oh well. Significance is all in the eyes of the beholders, and the more supporting evidence you have... the more people will see things as significant. One "general" way this may be achieved is by...

- Mon Apr 27, 2009 6:19 am UTC
- Forum: Mathematics
- Topic: Congruent regular hexagons and distinct compartments
- Replies:
**2** - Views:
**4564**

### Re: Congruent regular hexagons and distinct compartments

Here's one solution.

- Fri Apr 24, 2009 10:38 pm UTC
- Forum: Mathematics
- Topic: Balls and buckets problem
- Replies:
**3** - Views:
**741**

### Re: Balls and buckets problem

There are n buckets, each initially containing one ball. Balls are thrown, and must land in one of the buckets. The probability that a ball will land in a particular bucket is the ratio of the number of balls in that bucket to the total number of balls. How many balls must be thrown so that there i...

- Wed Apr 22, 2009 2:05 pm UTC
- Forum: Mathematics
- Topic: Simple trig function
- Replies:
**10** - Views:
**985**

### Re: Simple trig function

for some values of y you can find solutions, for example x=y=0 is a solution. for most y values though you'll likely be looking at a numerical scheme to approximate a solution.

- Tue Apr 21, 2009 4:04 am UTC
- Forum: Mathematics
- Topic: Simple Exponent Question (highschool math)
- Replies:
**11** - Views:
**1413**

### Re: Simple Exponent Question (highschool math)

Anyways, the question were were given was to write the expression 2 x + 5 as just 2 (?) (Two to the some exponent) This leads to the same answer as before but here's another way to find that answer. All you do is write down what you want. 2^x + 5= 2^{(?)} and solve for the (?...

- Mon Apr 20, 2009 2:25 am UTC
- Forum: Mathematics
- Topic: [Request] Cramer's Rule Help
- Replies:
**14** - Views:
**2307**

### Re: [Request] Cramer's Rule Help

What cramers rule is, is a way to solve a system of linear equations by turning it into a (generally) harder (to compute numerically) bunch of determinants, then doing some division. Since it's "harder" why use it, you may ask... Third paragraph in the wiki article gives a little answer to...

- Sun Apr 19, 2009 9:24 pm UTC
- Forum: Mathematics
- Topic: please help me with this prob I'm lazy
- Replies:
**4** - Views:
**869**

### Re: please help me with this prob I'm lazy

Re: please help me with this prob I'm lazy

I enjoy investing my time to help people most when they need the help because they are lazy. It's a waste of my time to help somebody that puts forth effort on their own.

- Sun Apr 19, 2009 6:20 pm UTC
- Forum: Mathematics
- Topic: Something I've been wondering...
- Replies:
**2** - Views:
**640**

### Re: Something I've been wondering...

The short answer is that when you add up infinitely many things (in this case the lengths of all your little pieces) strange things can happen. You're also dealing with two types of convergence. On the one hand your "staircase" is converging to the straight line. On the other, as you point...

- Sat Apr 11, 2009 6:56 am UTC
- Forum: Mathematics
- Topic: The MOST comprehensive math reference poster one can purchas
- Replies:
**18** - Views:
**2740**

### Re: The MOST comprehensive math reference poster one can purchas

A link would be lovely :D Other's have left good things since then but I fixed my post above to include the link I intended to leave the other day. Silly me. OP, what do you mean by "300-400 level math"? A practice that some schools in the US still follow is to list freshman level classes...

- Fri Apr 10, 2009 4:05 pm UTC
- Forum: Mathematics
- Topic: The MOST comprehensive math reference poster one can purchas
- Replies:
**18** - Views:
**2740**

### Re: The MOST comprehensive math reference poster one can purchas

Here's a link to a list of links that each have math posters of some sort or other. The ones I looked at don't seem to have quite what your looking for as a single poster, but maybe you can pick and choose a few of them to get the sort of spread of topics you want. edit: Well that was bad. As was po...

- Sat Apr 04, 2009 11:46 pm UTC
- Forum: Mathematics
- Topic: Pendulum question
- Replies:
**3** - Views:
**747**

### Re: Pendulum question

Don't forget though a pendulum is a dynamical system with some fixed points. As such the probabilities of being at certain angles depends on what time interval you are looking at and whether or not it's a forced pendulum. If it's not forced and you look at it a long time after it's initial condition...

- Sat Apr 04, 2009 4:43 pm UTC
- Forum: Mathematics
- Topic: Function extrema in general
- Replies:
**9** - Views:
**1613**

### Re: Function extrema in general

Uh, if x is in V , how can f(x) fail to be in f[V] ? I'm still trying to decode the rest of your definition, but this at least doesn't seem right to me. You're right I should have said fail to be in the interior of f(V)... or as bray mentioned I really should have just remembered the word b...

- Sat Apr 04, 2009 4:39 pm UTC
- Forum: Mathematics
- Topic: Differential Equations: Please Help.
- Replies:
**8** - Views:
**1312**

### Re: Differential Equations: Please Help.

the tree wrote:it's simply because all mathematicians are complete bastards who want to confuse you for thier own amusement.

Don't tell other people this. It's supposed to be a trade secret.

- Fri Apr 03, 2009 8:03 am UTC
- Forum: Mathematics
- Topic: Function extrema in general
- Replies:
**9** - Views:
**1613**

### Re: Function extrema in general

I don't think you need a partial order either... at least not to find extrema. As long as you don't want to classify them as "min" or "max" or somesuch I think what you might try using as the definition of x an extreme value for f is that every open set U containing x has an open...

- Wed Mar 25, 2009 6:42 am UTC
- Forum: Mathematics
- Topic: Laplace Transformations
- Replies:
**3** - Views:
**1033**

### Re: Laplace Transformations

A common "first use" for Laplace transforms is in differential equations. You can take a differential equation, transform it into an algebra equation, solve that, then transform your answer back.

- Mon Mar 23, 2009 4:33 am UTC
- Forum: Mathematics
- Topic: Cutting up apples
- Replies:
**9** - Views:
**1317**

### Re: Cutting up apples

at each step is the interval chosen uniformly and randomly from the k+n intervals or is the distribution actually on the numbers within the intervals. i.e. are bigger intervals more likely to be chosen or at step n does each interval have a 1 in n+k shot?

- Sat Mar 21, 2009 4:05 pm UTC
- Forum: Mathematics
- Topic: Uncountably many vertical asymptotes?
- Replies:
**18** - Views:
**2159**

### Re: Uncountably many vertical asymptotes?

Okay, suppose you have uncountably many left-vertical asymptotes, i.e. a set of numbers x i for i \in I (with I uncountable) so that the limit \lim_{x \rightarrow x_i^-} f(x) = \pm \infty . For each asymptote at x i , take an open interval (a_i,x_i) that contains no other asymptotes. (There...

- Thu Mar 19, 2009 6:41 am UTC
- Forum: Mathematics
- Topic: Here's a fun problem...
- Replies:
**27** - Views:
**3735**

### Re: Here's a fun problem...

(made by a association of mine) A man on the street asks you to play a game of chance; ...What amount of money should you be willing to pay to play the game? Nothing. If a random man on the street "offers" to let you play -- You should really assume that the game is either rigged or skewe...

- Fri Mar 13, 2009 5:23 pm UTC
- Forum: Mathematics
- Topic: Pi Day
- Replies:
**49** - Views:
**6179**

### Re: Pi Day

I honestly do not understand a how anyone can logically think dd/mm is good, and I would love to hear your reasons if you care to share. Three units of measure years, months and days that have a relation, namely 1year > 1 month > 1 day. So when saying all three it seems sensible to either say the b...

- Thu Mar 12, 2009 6:03 pm UTC
- Forum: Mathematics
- Topic: What is wrong with this differentiation?
- Replies:
**19** - Views:
**2851**

### Re: What is wrong with this differentiation?

Say what? Can you tell me what this is equal to? \sum\limits_{i=1}^{5/3}\sin{i} Using the method above set y(i)=3i and then \sum\limits_{i=1}^{5/3}\sin{i} = \sum_{y(1)=3}^{y\left(5/3\right)=5} \sin \left(\frac{y}{3}\right) = \sin\left(\frac{3}{3}\right)+\sin\...

- Thu Mar 12, 2009 4:05 am UTC
- Forum: Mathematics
- Topic: Fix My Broken Integration
- Replies:
**5** - Views:
**925**

### Re: Fix My Broken Integration

The Idea behind partial fraction decomposition still works. It's just (sometimes) much harder to find the correct numerators AND once you do find the correct numerators the two (or more) pieces you have are not always easy to integrate.