Search found 30 matches

by Coding
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."
by Coding
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...
by Coding
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. :)
by Coding
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...
by Coding
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...
by Coding
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. :)
by Coding
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.
by Coding
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...
by Coding
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." ...
by Coding
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.
by Coding
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...
by Coding
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, ...
by Coding
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.
by Coding
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 ...
by Coding
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...
by Coding
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...
by Coding
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.
by Coding
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...
by Coding
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...
by Coding
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...
by Coding
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 ...
by Coding
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."
by Coding
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. :)
by Coding
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).
by Coding
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...
by Coding
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. :)
by Coding
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...
by Coding
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...
by Coding
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?
by Coding
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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