## Search found 20 matches

- Mon Sep 10, 2012 4:02 pm UTC
- Forum: Mathematics
- Topic: Inexperienced proofer
- Replies:
**10** - Views:
**5528**

### Re: Inexperienced proofer

That's a good strategy. With set theory, another strategy that works a lot is a long one-line showing how two expressions are equivalent by symbolic manipulation of the definitions. The nice thing about that is that that all of those definitions are usually reversible so you can cover both halves o...

- Mon Sep 10, 2012 4:25 am UTC
- Forum: Mathematics
- Topic: Inexperienced proofer
- Replies:
**10** - Views:
**5528**

### Re: Inexperienced proofer

I'm just doing how I was taught to tackle proofs for showing two sets are equal. Show any element in set A is also an element of set B, then vice-versa.

- Mon Sep 10, 2012 2:29 am UTC
- Forum: Mathematics
- Topic: Inexperienced proofer
- Replies:
**10** - Views:
**5528**

### Re: Inexperienced proofer

This is what I ended up with: Assume (g o f)^-1 (H) < f^-1 (g^-1 (H)). Let x be in f^-1 (g^-1 (H)). The function (g o f)(x) takes elements x in A and tramsforms them into elements in C, by 1.1.12*. The inverse, (g o f)^-1 (H), takes elements in H<C, transforms them under the inage g^-1 ,then transfo...

- Sun Sep 09, 2012 11:52 pm UTC
- Forum: Mathematics
- Topic: Inexperienced proofer
- Replies:
**10** - Views:
**5528**

### Inexperienced proofer

Let f : A -> B and g : B -> C be functions and let H be a subset of C. Prove (g o f)-1 (H) = f-1 (g-1 (H)). I can try to prove they are subsets of each other or use a Not Q => Not P argument. The only lemma I have to work with is that f(g(x)) = (f o g)(x). My first attempt I started with "Let I...

- Thu May 12, 2011 4:47 am UTC
- Forum: Mathematics
- Topic: Sum of a series (test review)
- Replies:
**4** - Views:
**1046**

### Re: Sum of a series (test review)

Try some easier problems first: What is \sum_{n=0}^\infty nx^{n-1} ? (Hint: It's the derivative of something.) This would just be 1/(1-x)^2 right, since it would be the derivative of 1/(1-x) Okay, now what is \sum_{n=0}^\infty nx^n ? I guess when n's are coefficients it's throwing me off.. ...

- Thu May 12, 2011 2:41 am UTC
- Forum: Mathematics
- Topic: Sum of a series (test review)
- Replies:
**4** - Views:
**1046**

### Re: Sum of a series (test review)

We never reviewed anything about generating functions.. and the third derivative gives us the denominator is there something else I'm missing? Is the only way to approach this with g.f.?

- Thu May 12, 2011 1:50 am UTC
- Forum: Mathematics
- Topic: Sum of a series (test review)
- Replies:
**4** - Views:
**1046**

### Sum of a series (test review)

So this question popped up on an exam, and I couldn't get the second part. We won't be getting the exams back due to it being the end of the semester and I am pulling my hair out. For one hard problem, they give us the answer, but we have to prove that it equals the given answer. Kinda like how you ...

- Fri Apr 22, 2011 4:23 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0889: "Turtles"
- Replies:
**207** - Views:
**61088**

### Re: 0889: Turtles

in before this doesn't fit into romance sarcasm math or language

- Mon Apr 18, 2011 1:56 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0887: "Future Timeline"
- Replies:
**192** - Views:
**58305**

### Re: 0887: "Future Timeline"

what makes this creepy, is that today is my birthday and I am always stressed out about what the future is going to bring.. get out of my head randall!!

- Fri Apr 01, 2011 10:07 pm UTC
- Forum: Coding
- Topic: Noob Question: How to make an equation look simpler
- Replies:
**18** - Views:
**2942**

### Re: Noob Question: How to make a equation look simpler

Sorry for the miscommunication; it's actually required by my universities' coding standards to have the syntax simplified like this whenever possible. I've actually lost points on an assignment before using "n = n + 1" instead óf "n += 1".

- Fri Apr 01, 2011 9:53 pm UTC
- Forum: Coding
- Topic: Noob Question: How to make an equation look simpler
- Replies:
**18** - Views:
**2942**

### Noob Question: How to make an equation look simpler

Okay, I'm writing a code in Python that has to deal with the Collatz Conjecture, and I've come to the following piece: # above I have already error-checked n to be a positive integer while n != 1: if n % 2 == 0: n = n / 2 # which can be simplified into: # n /= 2 else: n = (n * 3) + 1 # but how can I...

- Wed Mar 30, 2011 4:14 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0879: "Lamp"
- Replies:
**151** - Views:
**37222**

### Re: 0879: "Lamp"

This was the first comic that made me laugh out loud in a long time.

- Mon Mar 07, 2011 5:01 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0869: "Server Attention Span"
- Replies:
**90** - Views:
**26158**

### 0869: "Server Attention Span"

http://imgs.xkcd.com/comics/server_attention_span.png Alt Text: "They have to keep the adjacent rack units empty. Otherwise, half the entries in their /var/log/syslog are just 'SERVER BELOW TRYING TO START CONVERSATION *AGAIN*.' and 'WISH THEY'D STOP GIVING HIM SO MUCH COFFEE IT SPLATTERS EVER...

- Thu Jan 13, 2011 7:40 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0846: "Dental Nerve"
- Replies:
**135** - Views:
**37029**

### Re: 0846: "Dental Nerve"

http://en.wikipedia.org/wiki/Kesha 1500 on her SAT. Supposedly. I'm actually pretty sure she's retarded. I don't care if the song's a joke, you wrote it. People sing it and they think you mean it because they're retarded. Why would she do this to us?!? I believe that 1500 is the combined score she ...

- Wed Jan 12, 2011 9:50 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0846: "Dental Nerve"
- Replies:
**135** - Views:
**37029**

### Re: 0846: "Dental Nerve"

There are quite a few songs based on dental hygiene. Like this one.

- Wed Dec 22, 2010 5:43 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0837: "Coupon Code"
- Replies:
**86** - Views:
**28765**

### Re: 0837: Coupon Code

Werewolf wrote:Epic win.

If I start an online site, I am putting that as an automatic coupon code.

Really? If you do, I'll buy everything

Does anyone else see the coupon code box as an opportunity, and then google the website + "coupon codes" ?

- Tue Apr 06, 2010 6:40 pm UTC
- Forum: Mathematics
- Topic: Calculus Test (Antiderivatives, etc)
- Replies:
**12** - Views:
**2595**

### Re: Calculus Test (Antiderivatives, etc)

@achan1058 Thanks, I'll take a look at those programs. =] @Qaanol lol thanks =] I am actually looking forward to learning how to make the maths look pretty. Also, I appreciate pointing out some of the errors. Making x=u+1 was probably me just running out of time on the test, but I think I solved the...

- Tue Apr 06, 2010 4:28 am UTC
- Forum: Mathematics
- Topic: Calculus Test (Antiderivatives, etc)
- Replies:
**12** - Views:
**2595**

### Re: Calculus Test (Antiderivatives, etc)

For the "fancy math" you'll probably want to check out this thread http://forums.xkcd.com/viewtopic.php?f=17&t=21939 and just learn a little latex in general. If you're a math person then Latex will become quite handy for you. Also, it'd be nice if you posted your work for the problem...

- Tue Apr 06, 2010 4:15 am UTC
- Forum: Mathematics
- Topic: Calculus Test (Antiderivatives, etc)
- Replies:
**12** - Views:
**2595**

### Re: Calculus Test (Antiderivatives, etc)

Also, if anyone has any advice on a program that will help me out with using the math tags, that'd be pretty cool too. Being able to actually post the integral symbol, sigma, etc would be extremely helpful. =]

- Tue Apr 06, 2010 4:10 am UTC
- Forum: Mathematics
- Topic: Calculus Test (Antiderivatives, etc)
- Replies:
**12** - Views:
**2595**

### Calculus Test (Antiderivatives, etc)

So I got my Calculus test back from my teacher and I wanted to know why some of these problems were wrong. 50 problems, 6 wrong. Not too bad, but, eh. I re-looked over my work and for some of them I can't figure out where my mistake was. The unit is done and over with, but, I want to make sure I do ...