## Longitude lines in perspective, what shape are they?

I'm drawing/painting a globe (in time lapse, so the sun appears to rise) and trying to figure out what shape, exactly, the longitude (not latitude) lines are when a globe is flattened into a circle (I know I can just trace them, but I've gotten curious). So, the outermost longitude lines are tangent to the circle, they are half-circles, and the centermost line is a straight line from pole to pole, it's the progressively flatter curves in between that I'm trying to figure out. Do they have a name? Are they catenaries? Are they the curves of progressively larger circles? How do I construct them (easily)? Example image: HERE
posted by sexyrobot on Jul 26, 2013 - 11 answers

## Not my high school TI-82.

I'm taking Calc I this fall. I can borrow a graphing calculator for actual exams, but don't want to actually purchase one for day-to-day--or haul it around with me. I have an iPhone and a Nexus 7. Is there a graphing calculator app in one or the other app store that is clearly superior? I'm willing to pay, but under \$10, ideally.
posted by Sequence on Jul 25, 2013 - 11 answers

## Where can I find sample arithmetic problems like this one!

I'm taking a standardized test on Wednesday with the Government of Canada and they ask individuals four types of questions. The type that I struggle with are the arithmetic problems... specifically determining the formulas to solve word problems. I was hoping someone might be able to point me in the direction of a website or easily accessible textbook to practice today and tomorrow before the test.
posted by DorothySmith on Jul 15, 2013 - 11 answers

## I was banned from collegeconfidential just for asking for some help?

Summer vacations are coming up and I am going to use some of my free time to learn physics and math, subjects that I love. In order to do that i asked collegeconfidential.com if anyone had "exclusive study materials" from their university which they could share. I mentioned that I would like to have acess to tests and exams from other universities and I could give some good materials collected by my colleagues of the physics and math course in exchange.
posted by tsuwal on Jul 12, 2013 - 27 answers

## Best option for completing two college math courses

What is the best option for a working professional to complete two undergraduate level math courses - linear algebra and differential equations - in order to bolster my graduate school application?
posted by nowoutside on Jun 30, 2013 - 8 answers

## Textbook Cross-reference for different editions

Is there some place I can find cross-reference guides to match up material and problem sets between different editions of the same textbook (specifically math textbooks) ?
posted by marsha56 on Jun 29, 2013 - 4 answers

## Help me convert this graph into a table.

I have a bitmap of a chart (in polar coordinates) that I would like to convert into a format that some plotting package can recognize, and then retrieve values from the chart at specific intervals. How do I do this?
posted by tylerkaraszewski on Jun 28, 2013 - 7 answers

So I am trying to figure out how to charge for a product that is a semi-circle. I charge per square feet. The client ordered a product that was 25 feet in diameter and 6 feet deep (radius if it were a full circle), then changed it to 20 feet in diameter and 10 feet deep (radius if it were a full circle. I tried to figure out the area of the space as half of 3.14 x radius squared. But there is no part of the equation accounting for the change in diameter... a little confused since this is the first time we are doing a semi circle. I feel like the it shouldn't work out to the same price. If I were charging \$1 per square foot, what would the difference in price be?
posted by soooo on Jun 26, 2013 - 24 answers

## iPad math apps for a 10-year-old?

My son is 10 years old and going into 5th grade in the fall (but he usually does 6th grade math). He likes Stack the States, and we're looking for a math app with similar appeal. We already have Sushi Monster and his younger sister loves it, but I'd like something more challenging for him.
posted by The corpse in the library on Jun 25, 2013 - 11 answers

## Find standard deviation in Excel, but first develop a labor-saving trick

Help me with statistics and Excel. Especially help me if you know any labor saving methods. I want the median, mean and standard deviation for the average price of all items sold, but my spreadsheet-full-of-data doesn't tell me the price of each sale -- just the average price per store, and the number sold at that store. Something like this:
posted by croutonsupafreak on Jun 21, 2013 - 10 answers

## Help me understand fractions

posted by anonymous on Jun 19, 2013 - 29 answers

## Returning to grad school after 2 year hiatus

So I'm beginning a statistics PhD program this fall and I'm concerned that my math skills have gotten rusty since I haven't done anything related for the past two years. I've been working as an actuary since I graduated college but I don't do that much math--mostly a lot of programming. Has anybody been in a similar situation to me? How was the adjustment for you? I'm considering retaking advanced calculus and linear algebra during my first year (probably next summer before I take 2nd year advanced courses) just to refresh myself again. I'm aware some people may think this is kind of pathetic but I'd rather be safe than sorry. Besides, it's only my first year. Is this frowned upon?
posted by molamola on Jun 17, 2013 - 15 answers

## Scale my function for a line graph

Math-filter: I have a line chart in Google Docs that plots three columns of data over time. Data in the first two columns ranges from 0-1000, but data in the third column ranges from 3-9. I'd like to "scale" Line 3 (maybe this is the wrong word?) to be able to compare its value over the same graph space as Lines 1 and 2.
posted by electric_counterpoint on Jun 12, 2013 - 7 answers

## Educate me on modern mathematics!

My math knowledge ends just past Newton. What books provide a good, relatively general-audience introduction to the past 150-250 years of problems and developments in mathematics?
posted by gallusgallus on Jun 10, 2013 - 7 answers

## I would rather throw a tantrum than learn math (10 year old edition)

I tutor a boy who is moving from 4th-5th grade. He's at grade level in most subjects, above grade level in reading, but getting an Elvis Presley head in math. Can you help me find ways to help him be less intimidated by math, allowing us more time to learn and practice before his eventual mental shutdown each session?
posted by ovenmitt on Jun 9, 2013 - 13 answers

## Learning Statistics for the Social Sciences 101 paperlessly

I'm running into trouble with my statistics course. I'm just getting up to t statistics for independent measures research design. My problems are: 1. I'm going through a lot of paper 2. I need to keep all my calculations better organized as a do them 3. I'm flipping back and forth between my book, an online version of the book, and another screen so that I can reference as much material as possible at once. I'm thinking some kind of basic statistics calculator spreadsheet (or any other format) would be in order. Can anybody direct me towards one?
posted by Che boludo! on Jun 8, 2013 - 9 answers

## Dealing with percentages: noob question

I've recently decided to transition to a new career path, accounting. Most firms round here do an online numeracy test as part of the application process. There is a type of % change question that often comes up and I can't find a proper answer about how to calculate it. There are two formulae suggested by different websites, but they give different answers. Which is right? (details inside)
posted by NoiselessPenguin on May 28, 2013 - 10 answers

## 150 to around 120, which bpm is best for pitch?

I have a song at 150 bpm, perfectly in tune. I want to repitch it down to around 120 by slowing it down. At which bpms will the notes be at pitch?
posted by semaphore on May 23, 2013 - 6 answers

## How do I go from one kind of nerd to another?

What steps should I take to switch to the aerospace industry from the academic world?
posted by vernondalhart on May 21, 2013 - 9 answers

## How to pronounce an equation in English.

Please help me pronounce this formula related to projectile motion as it would be spoken out loud: L = v0^2 sin2θ / g
posted by misozaki on Apr 30, 2013 - 15 answers

## How can I relearn high school subjects?

I want to relearn algebra, chemistry, basic mechanics, and basic physics this summer. For free?
posted by Grandysaur on Apr 25, 2013 - 12 answers

## Tweak my study habits.

I'm taking Calc II at a community college and I'm not getting the grades I want. Studying 10 hours everyday a week in advance only got me an 84% on the first test. It is clear that I'm doing something wrong, but what is it? Help me tweak my study habits before the second test!
posted by squirtle on Apr 10, 2013 - 18 answers

## Algebra: exotic identity values?

[mathfilter] please give me some example algebraic structures that are not commutative, with exotic identity values.
posted by knz on Apr 8, 2013 - 5 answers

## Masters in maths? Difficulty level: Have bachelors in graphic design

Dear Mefites, a long time ago I got a degree in graphic design but never worked in the industry. Along the way I somehow (don't remember how or why or when) became interested in math and I finished a graduate diploma in maths as a distance learning course in my free time. I am considering applying for masters programmes in maths or related subjects but ... can I? Should I?
posted by Cat Set Go on Mar 31, 2013 - 10 answers

## Wearable expressions

What is the math (physics?) going on in this very cool-looking, equations-as-art necklace?
posted by firstbest on Mar 28, 2013 - 10 answers

## I can say with 99% confidence that this class is killing me

I'm struggling hard in my statistics class right now. Some of it comes from not grasping the concepts, but a bigger part is the ridiculous level of anxiety I've developed about my grades, and catastrophizing about what a low grade means. Help me attack both aspects of the problem.
posted by ActionPopulated on Mar 28, 2013 - 22 answers

## I can't do basic math, but my competence is in other things...Help?

We want to assess a list of vendors in two domains: Accessibility and Cost. We have two tools that we are using to essentially score them in each of these domains separately. The Accessibility assessment tool totals 110 points; the Cost tool totals 90 points. We want a final score for each vendor that combines the domains and is out of 100. We want the Accessibility score to "count" about 20% more than the Cost score in the final because it is more important to us. How do we do this?
posted by OmieWise on Mar 14, 2013 - 10 answers

## Basic math test as part of a job application?

Which employers still use a basic math test as part of the application process?
posted by klausman on Mar 9, 2013 - 15 answers

## Math/Physics Question: Stability of an abruptly stopped object

If you have an object with a given base length and a given CG height, how fast can it travel before you have to worry about it running over an obstacle and falling over?
posted by Popular Ethics on Mar 5, 2013 - 16 answers

## How to study math

What is the best way to manage time while studying for upper-division undergraduate math classes that are proof-based/STEM classes in general?
posted by Hey Judas! on Mar 5, 2013 - 15 answers

## Can a transcendental number raised to an algebraic power be algebraic?

Can a transcendental number such as pi, be raised to an irrational, but algebraic power resulting in an algebraic solution? Complex solutions would be acceptable. There might be a quick proof here, or there might not be. - Thanks for any help you can offer answering this! (And I promise that this isn't for a class or anything like that!)
posted by ch3cooh on Mar 2, 2013 - 3 answers

## Books about mathematics for the interested layman?

So, physicists like Brian Greene, Lisa Randall, Kip Thorne, and others have written books aimed at an interested lay audience. What are similar books written by mathematicians? I'm aware of Godel, Escher & Bach. And that's about it.
posted by dfriedman on Feb 25, 2013 - 23 answers

## Explain the Riemann-Christoffel curvature tensor

Greetings Ask Metafilter: Can anyone suggest a book or article that provides a simple, yet comprehensive explanation of the Riemann-Christoffel curvature tensor? I've studied the explanation provided by Lillian Lieber in her book The Einstein Theory of Relativity, but for several reasons I am suspicious of the validity of her derivation, and her claim that the tensor can be used to distinguish between Euclidean and non-Euclidean space. Lieber gives the Rieman-Christoffel curvature as follows: {σρ,ε} {ετ,α}- ∂/(∂x_ρ ) {στ,α}+∂/(∂x_τ ) {σρ,α}-{στ,ε} {ερ,α} Lieber derives the curvature tensor from a covariant tensor of rank one that has undergone two different sequences of covariant differentiation. This supposedly produces two different versions of the second, partial, covariant derivative of a covariant tensor of rank one.
posted by jesman on Feb 14, 2013 - 4 answers

## Fiction help: Name something a math genius could do to improve a bar.

Writing a script, need a few believable, throwaway lines for a character. A guy running a TGI.Friday's-like bar praises his bartender, a math genius, for giving him an idea that saves money and improves the business overall. An example of outside-of-the-box thinking that enforces that our math-genius-in-disguise really is a genius. Bonus points if the idea skirts the line of legality -- something funky with accounting, maybe?
posted by Cool Papa Bell on Feb 9, 2013 - 22 answers

## How do I learn to be an effective tutor?

If I know the material that I'm teaching well, but don't have any experience with tutoring or teaching, how do I learn the skills and techniques that will help me be an effective tutor?
posted by cognitio on Feb 3, 2013 - 8 answers

## Clearly, this proves that I'm stupid

I can't seem to wrap my mind around the language of higher level math. Definitions, theorems, and proofs make me fall asleep, but I really do want to understand. Do you know of any good resources that can help me out?
posted by lucia_engel on Jan 31, 2013 - 19 answers

## The Seven Bridges of Königsberg in 200 Words or Less

Can you recommend short, easy-to-understand math writing I can read before bed?
posted by kristi on Jan 29, 2013 - 12 answers

## Fallacies and Errors in Inferential Statistics

I have recently been introduced to the concept of pseudoreplication as a mistake that people often make when using inferential statistics to evaluate treatment outcomes. My field (evolutionary and conservation biology) makes heavy use of inferential statistics, including techniques that are vulnerable to pseudoreplication, yet nowhere in my formal education have I been taught about how poor experimental design and lack of statistical rigor can lead to fallacies like this. My personal statistical proficiency is poor, but I am working to remedy that. To that end, could folks help me by identifying and ideally explaining whatever other potential pitfalls you can think of, and explaining how they can be avoided through careful experimental design and data-analysis?
posted by Scientist on Jan 26, 2013 - 5 answers

## What does a mathematician do all day?

I'm wondering, after breakfast, and a shower, and a commute, and coffee - what is next?
posted by Lownotes on Jan 24, 2013 - 23 answers

## How do I figure out how to divvy out these projects?

I have roughly 20 people who each need a project. I have 27 projects and don't want anyone to share a project. I let the people pick their top five projects and rank them so I know who wants what. What is the best (easiest...) way for me to fairly figure out who should get what project so that the most people get their top choice, or at least one of their top choices?
posted by pwb503 on Jan 22, 2013 - 8 answers

## The heck is a modular form?

For a work assignment, I need to come by a conceptual understanding of modular forms that's light on jargon and, ahem, actual math. If such a thing is possible.
posted by Zerowensboring on Jan 18, 2013 - 12 answers

## Teach myself Math virtually for the first time.

I'm a 21 year old college senior liberal arts major who has managed to slide by in school (and life) without ever really learning math beyond a middle school/very early high school level. For no reason in particular, I've decided that I want to get serious about bettering myself in the math department. How can I teach myself the academic math skills I missed out on?
posted by Krazor on Jan 15, 2013 - 19 answers

## Online Math Tutor

I'm a college student who is having some issues really understanding Calculus II, which is a problem as A) I am a Comp Sci major, and B) I need to take Calc III as well, and an advanced math elective as well. I've not heard good things about the school provided tutors, (IE, one is not too skilled at math, and the other is really smug and poor pedagogically) and while I could get a private tutor to help me, I was wondering if there are any good resources for online math tutors, like there are for online language tutoring over Skype. Does a directory of such tutors exist, has anyone had a good experience doing this (maybe even with names?), and how much can I expect to pay?
posted by mccarty.tim on Jan 14, 2013 - 11 answers

## Perspective drawing calculation

If I want to draw something in one-point perspective, say, like a set of railroad tracks where the vanishing point is on the horizon, and the tracks are represented on the picture plane by an equilateral triangle (they appear that way to the viewer), the apex of the triangle being the vanishing point on the horizon and the base of the triangle is where the tracks meet the picture plane, how do I calculate where the railroad ties would be? (Given that in 3D they are evenly spaced. Also, I'm not really concerned with the thickness of the ties -- we can consider the ties to simply be horizontal lines.)
posted by strangeguitars on Jan 8, 2013 - 5 answers

## Teach me about Applied Math

I'm interested in a Masters in Applied Mathematics in the NYC area. Help me research further.
posted by prunes on Jan 1, 2013 - 7 answers

## Weighted mean

Mathematics-filter: If there are seven funds with various charges, how can I work out the allocation to these funds of a fixed amount so that the weighted mean charge is below a certain level and the allocations are of similar sizes?
posted by djgh on Dec 31, 2012 - 13 answers

## The use of Linear Algebra in Programming.

I just finished my first course in Linear Algebra. I know a fair amount of Python. Please help me come up with a project that combines the two.
posted by lobbyist on Dec 23, 2012 - 11 answers

## Can't do ALL THE THINGS right now.

In 2013 I will have 2-3 hours a week to spend learning one or more of the following: French, guitar, advanced math (stats, calc). Which will benefit most from this limited amount of study effort?
posted by riddler on Dec 15, 2012 - 6 answers

## centering circular cake boards

[geometryfilter] I have to assemble a tiered cake stand to hold cupcakes at a wedding tomorrow. The tiers and the styrofoam thingies that will separate the tiers are all circular. How do I make sure that I get each tier centered properly on the next?
posted by undue influence on Dec 13, 2012 - 5 answers

## If I Knew the Answer, I Could Probably Give the Question a Good Title

Is there a formula for determining (eg.) how many tracks would fit on a TT 79:57 CDR where the first track was one second, and subsequent tracks added 1 second each? (00:01, 00:02, 00:03, 00:04, &c)
posted by herbplarfegan on Dec 10, 2012 - 7 answers

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