## Search found 30 matches

Sat Jul 14, 2012 1:41 am UTC
Forum: News & Articles
Topic: Look who else rape culture is hurting
Replies: 88
Views: 15630

### Re: Look who else rape culture is hurting

Criminals in general? No. But I would think it a bit "off" if I heard an actor say, "You know, I really love playing rapists in my films, especially when I get to do a rape scene."
Sat Jul 07, 2012 8:28 pm UTC
Forum: General
Topic: Have You Ever Taken Drugs?
Replies: 287
Views: 35188

### Re: Have You Ever Taken Drugs?

Meth was developed to stave off fatigue among soldiers. A role in which it was supposedly pretty effective, though with worse side effects than its younger cousins like dexedrine (aka Adderall). PCP was originally an anesthetic, but like other NMDA receptor antagonists (ketamine, DXM) it can cause s...
Sun Apr 15, 2012 1:23 am UTC
Forum: School
Topic: Going to High School, need help finding a passion....
Replies: 20
Views: 6788

### Re: Going to High School, need help finding a passion....

As someone with a BA in philosophy, I personally suggest...looking into mathematics.
Sat Apr 14, 2012 6:29 pm UTC
Forum: Mathematics
Topic: Limit of a series
Replies: 26
Views: 6048

### Re: Limit of a series

For amusement, you can use the same technique to show that 1 - 1/2 + 1/3 - 1/4 + ... converges, since the terms here are grouped like \frac{1}{2n} - \frac{1}{2n+1} = \frac{1}{4n^2 + 2n} which converges by the limit comparison test. I was kind of confused on seeing this, since you had the even-denom...
Sat Apr 14, 2012 7:47 am UTC
Forum: Mathematics
Topic: Limit of a series
Replies: 26
Views: 6048

### Re: Limit of a series

So, I knew that the alternating harmonic series converges and now learned (from the answers above) that the series Dopefish posted diverges, which makes me wonder about the more general question: does any harmonic series in which less than half the signs are negative diverge (given that the signs ar...
Fri Apr 13, 2012 1:45 pm UTC
Forum: Mathematics
Topic: Summation
Replies: 6
Views: 1643

### Re: Summation

Now that gorcee and gmalivuk have posted the formula for the summation, you can try proving that it holds for any natural number n. If you are interested in that sort of thing, anyway.
Thu Apr 12, 2012 11:07 pm UTC
Forum: Mathematics
Topic: Is this right? (improper integral)
Replies: 4
Views: 1866

### Re: Is this right? (improper integral)

Yeah, good point. Thanks.
Thu Apr 12, 2012 10:46 pm UTC
Forum: Mathematics
Topic: Is this right? (improper integral)
Replies: 4
Views: 1866

### Is this right? (improper integral)

Not homework, just seemed like a neat problem to me (saw just the conclusion stated in a textbook, and decided to try to get it myself; I'm currently in Calc II). \int_{0}^{\infty} x^k e^{-x}dx Now I use the indefinite integral and integrate by parts, with u=x k and dv=e -x dx: \int x^k e^{-x}dx = x...
Wed Apr 11, 2012 2:08 am UTC
Forum: Mathematics
Topic: Guess the sequence.
Replies: 25
Views: 7437

### Re: Guess the sequence.

Ben-oni 1: 1, 11, 21, 1211, 111221, 312211, 13112221, ... Continuation: 1113213211, 31131211131221... f(0) = 1. Take previous string s of digits. For each sub-string s of repeated digit d, write length of s followed by d. Ex. "1" has one "1," so we write "11." ...
Fri Apr 06, 2012 11:09 pm UTC
Forum: Mathematics
Topic: Favorite number sequences?
Replies: 24
Views: 4267

### Re: Favorite number sequences?

Fibonacci and relatives (tribonacci, tetranacci, etc.) are pretty cool. I am also a bit partial to sequences that I "discovered" on my own before reading about them or anything, so I like the free polyomino sequence and the triangular numbers.
Sun Apr 01, 2012 7:16 pm UTC
Forum: Mathematics
Topic: Function converges to square root, but why?
Replies: 7
Views: 3831

### Re: Function converges to square root, but why?

The usual trick with recursive series like this is to just substitute the same variable x or something for all instances of f(n-1) etc. so in this case you get: x = \frac{a}{x} + \frac{b}{x} and solving for x gives you x=sqrt(a+b) So if the series does indeed converge that (+-) is what it i...
Sun Apr 01, 2012 6:06 pm UTC
Forum: Mathematics
Topic: Function converges to square root, but why?
Replies: 7
Views: 3831

### Function converges to square root, but why?

I think the Fibonacci sequence is neat, so today I made this up: f(1) = f(2) = 1 f(n) = \frac{1}{f(n-1)} + \frac{1}{f(n-2)} I plug it into a program and get: 2.0 1.5 1.16666666666667 1.52380952380952 1.51339285714286 1.31701696165192 ... 1.41422484178857 Hey, ...
Wed Mar 28, 2012 3:10 am UTC
Forum: Mathematics
Topic: Being Fast At Calculation
Replies: 14
Views: 3187

### Re: Being Fast At Calculation

240 - 24 would be my go-to method. Subtracting from a multiple of ten is pretty fast for me.
Wed Mar 21, 2012 1:47 pm UTC
Forum: Mathematics
Topic: Exponential versus factorial
Replies: 3
Views: 2779

### Exponential versus factorial

Define f(k) as the lowest natural number n such that n! > k n . For example, f(2) would give you 4, since 3! < 2 3 but 4! > 2 4 . Obviously f(k) grows larger as k itself grows larger. I was wondering whether f(k) / k would approach some value as k -> infinity, and OEIS tells me that it does: e. But ...
Thu Feb 09, 2012 8:19 pm UTC
Forum: Mathematics
Topic: Largest 3 consecutive semi-primes?
Replies: 19
Views: 6089

### Re: Largest 3 consecutive semi-primes?

Larger ones that work: 201, 202, 203, 213, 214, 215, 217, 218, 219, 301, 302, 303, 393, 394, 395, 445, 446, 447, 633, 634, 635, 697, 698, 699, 841, 842, 843, 921, 922, 923, 1041, 1042, 1043, 1137, 1138, 1139, 1261, 1262, 1263, 1345, 1346, 1347, 1401, 1402, 1403, 1641, 1642, 1643, 1761, 1762, 1763, 1...
Sat Nov 26, 2011 5:45 pm UTC
Forum: School
Topic: High School Reunion
Replies: 18
Views: 4166

### Re: Reunion

My ten year reunion, assuming there is one planned, will be in two years. I feel old now. Personally I am quite skeptical that I have things more together than anyone else, since I know what a number of them have done since high school. One well on the way to being a neuroscientist, another in the S...
Sun Oct 30, 2011 5:44 pm UTC
Forum: Books
Topic: Mitchell Heisman's Suicide Note
Replies: 2
Views: 3313

### Re: Mitchell Heisman's Suicide Note

I read the first few pages a while back and was rather unimpressed. Maybe I will give it another look, though.
Mon Oct 24, 2011 2:05 pm UTC
Forum: General
Topic: Random encounters years later
Replies: 12
Views: 2772

### Random encounters years later

I have a new boss at work. She looked familiar to me from the start, but I couldn't place her until I learned her name today and thought, "That looks just like [x] from my club swim team ten years ago!" I thought that it might just be a coincidence, since today I live over a thousand miles...
Fri Oct 21, 2011 3:10 am UTC
Forum: Mathematics
Topic: Cantor's Diagonalization Proof
Replies: 314
Views: 19409

### Re: Cantor's Diagonalization Proof

I don't see any other way to phrase it. Every time I try to make sense of the bijection/set-dependent line of argument, I get tripped up by the "all reals are in R, except they aren't when we want to show that 1:1 correspondence isn't possible" step. No, all reals are always in R. Like an...
Thu Oct 20, 2011 3:44 pm UTC
Forum: Mathematics
Topic: Cantor's Diagonalization Proof
Replies: 314
Views: 19409

### Re: Cantor's Diagonalization Proof

There's often a similar problem with people trying to understand the proof by contradiction that proves there are infinitely many primes. You show that, assuming there are only a finite number of primes, then the product of all of those primes plus one is a new prime and so the assumption made at t...
Thu Oct 20, 2011 1:09 am UTC
Forum: General
Topic: Confessional Shed - I'll keep a look-out
Replies: 38049
Views: 2811336

### Re: Confessional Shed - I'll keep a look-out

I'm scared to death of taking the SAT. I don't know why. The deadline is tomorrow, and I still haven't signed up for it. (There's late registration though.) I'm 21 and what I'm doing now will get me nowhere satisfying in life. I consider myself fairly smart, so why can't I get over this irrational ...
Tue Oct 18, 2011 11:44 pm UTC
Forum: Mathematics
Topic: A Semantic Survey
Replies: 17
Views: 2351

### Re: A Semantic Survey

I read it as "none of the cards are hearts" (or "all of the cards are non-heart cards").

I would read "not all three of the cards are hearts" as "at least one of the cards is a non-heart card."
Sun Sep 25, 2011 11:42 pm UTC
Forum: Mathematics
Topic: euler's number
Replies: 16
Views: 3684

### Re: euler's number

Cool, thanks a lot to all three of you.
Sun Sep 25, 2011 9:06 pm UTC
Forum: Mathematics
Topic: euler's number
Replies: 16
Views: 3684

### Re: euler's number

Now that the OP has figured out his solution, can someone be kind enough to write out a full proof of the limit? I have just started learning proofs and feel like it would be instructive to see (and I already tried working it out on my own but got nowhere).
Fri Sep 23, 2011 1:00 am UTC
Forum: Mathematics
Topic: Illogical Standardized Testing Logic Problem
Replies: 13
Views: 1931

### Re: Illogical Standardized Testing Logic Problem

What book are you guys using, by the way? My girlfriend (law student) is curious. :) McGraw-Hill's Conquering LSAT Logic Games 2nd Edition . This problem can be found on page 18. Well, the Amazon review page does not exactly inspire confidence: http://www.amazon.com/McGraw-Hills-Conquering-LSAT-Log...
Thu Sep 22, 2011 10:51 pm UTC
Forum: Mathematics
Topic: Illogical Standardized Testing Logic Problem
Replies: 13
Views: 1931

### Re: Illogical Standardized Testing Logic Problem

What book are you guys using, by the way? My girlfriend (law student) is curious.
Thu Sep 22, 2011 10:22 pm UTC
Forum: Mathematics
Topic: Illogical Standardized Testing Logic Problem
Replies: 13
Views: 1931

### Re: Illogical Standardized Testing Logic Problem

!H -> E D -> (F & A & C) G -> !E A -> (B & F & G) We are given !G ("not G"). (1) is clearly wrong, as if we have A, then it follows that G is also true, which would contradict our given, !G. (2) could be right. (3) is also wrong, because if we have D, then we also have A, w...
Tue Sep 20, 2011 12:09 am UTC
Forum: Mathematics
Topic: Why do "secant" lines and "1/cos" share a name?
Replies: 11
Views: 6105

### Re: Why do "secant" lines and "1/cos" share a name?

Interesting. Thanks! I don't think I had ever used secants or cosecants of circles in any substantive way, so I had never thought about them beyond just translating them into "1 / cos" and "1 / sin" for homework and tests. Never learned to visualize them like cosine, sine, and ta...
Mon Sep 19, 2011 9:05 pm UTC
Forum: Mathematics
Topic: Why do "secant" lines and "1/cos" share a name?
Replies: 11
Views: 6105

### Why do "secant" lines and "1/cos" share a name?

I asked my calculus instructor this question, and she was unsure.

Can anyone enlighten me on the relationship (if any) between the trig functions like secant and tangent, and their correspondingly named lines in geometry / calculus?
Thu Sep 15, 2011 7:09 pm UTC
Forum: Mathematics
Topic: Proof By Induction
Replies: 13
Views: 2024

### Re: Proof By Induction

That sounds like a passage from What Is Mathematics? by Courant and Robbins. Is that one of the books you were reading. Induction allows you to prove that a statement P is true of a collection of objects by proving two sub-statements of the form: 1. If P n is true, then P n+1 is true. 2. P 0 is true...

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