English – Page 11 – Mathemafrica

The Varsity Maths Problem

The following post is written by John Webb from The Department of Mathematics and Applied Mathematics at The University of Cape Town. With his permission I include it here as an advert for a book which is discussed at the bottom of the post. Mathemafrica receives no payment for including this text. I hope that in addition to being an advert for the book, this may be a chance for students to discuss some of the problems they see with the transition between school and University here in South Africa for maths students.

Why do so many first-year students fail varsity maths?
Thousands of students across South Africa have started their university careers, and many of them have enrolled for a course in Mathematics. Some will be aiming at a maths major, in particular those who hope to teach mathematics at school level. But far more will be doing maths as a requirement for their degrees in a whole range of areas.…

By Jonathan Shock| June 3rd, 2015|Background, English, Level: Simple|4 Comments

Cooking with Mathematics

This post is not going to be very maths-heavy but will include some concepts from the area of graph theory which we will use in an unusual setting.

Today we’re going to get into the virtual kitchen and get our virtual taste buds a-buzzing….Well, actually we’re going to get our computers to do the hard work of finding out some tasty recipes and we’re going to use a few different techniques to do this. The workhorse is going to be the Mathematica programming language, but a lot of what we will do will be doable in any programming language, though perhaps it will be slightly more cumbersome than this.

The starting point of our culinary adventure will be a piece of text, taken from a website of flavour pairings here.

We see here that we have a piece of text which we can copy and paste into our Mathematica file.…

By Jonathan Shock| May 31st, 2015|English, Level: intermediate|6 Comments

A Mathematics Problem from the SBITC

The Standard Bank IT Challenge (SBITC) is an annual coding competition for undergraduate and honours students in South Africa. The contest consists of two rounds: a regional event named the “heats”, and the final. In the heats, teams of up to four students each compete against other teams from the same university, and the winning team from each of the nine top-performing universities is invited to the final round in Johannesburg. Each member of the winning team wins a prize, and the winning university receives a large cash prize, but students mostly participate for the enjoyment that is to be obtained in solving the problems, and to test their skills against a set of problems that is designed to challenge the participants.

This year, the final problem from the heats (which took place on Saturday, 16 May) was fairly mathematical in nature; or more-so than the other problems at least. Essentially, the problem asks the following:

We consider generalised Fibonacci sequences $T_n$ which satisfy the same recurrence relation $T_{n + 2} = T_{n + 1} + T_n$ as the Fibonacci numbers, but with the first two terms $T_1$ and $T_2$ being arbitrary positive integers.…

By Dylan Nelson| May 29th, 2015|English, Level: intermediate, Uncategorized|0 Comments

Mathematics or dreams, which is more real?

Mathematics can sometimes seem dream-like, at least on first encounter. Later on, one gets
used to a new mathematical object, and it seems everyday. I remember how strange the idea of
a group was to me, how mysteriously it grew from three almost trivial axioms to a forest
of subgroups and quotient groups and equivalence classes and so on. Of the few dreams I
now recall, there was one with a huge hall full of people, perhaps a giant cave, and I was descending a long,
rickety staircase — or was I sliding down a cable? — feeling myself among a heretofore
completely unsuspected part of humanity, who perhaps nobody from above ground had ever seen.
Groups were a bit like that, and saying that a square had a symmetery group did not
make them appear any less unexpected.

Furthermore, dreams and mathematics have a lot in common—I mean here the dreams that
people, when awake, remember having had when asleep.…

By Henri Laurie| April 13th, 2015|Background, English, Level: Simple|2 Comments

AIMS-IMAGINARY Workshop 2014

A little blog about the conference in which Mathemafrica was conceived! This first appeared on the ICTP math blog on the 18th of November 2014.

One of the perks of working in mathematics is that I get to travel the world as part of my job. This time it was Cape Town, South Africa; I flew down there to participate in a workshop on maths `outreach’ activities in Africa. The workshop was held at the African Institute for Mathematical Sciences (AIMS) and was organised in partnership with IMAGINARY. Will introduce the organisers in a bit but let me focus on the idea of mathematics outreach for now.

For me, mathematics outreach is an attempt to share mathematical ideas with non-experts in the field. The term non-expert includes a broad spectrum of people stretching from school children to senior citizens. Math-outreach is usually done through exhibitions and the written media but the definition allows for many more forms of communication.…

By Tarig| March 15th, 2015|English, Event|1 Comment

An explanation for the multiplier effect in a Keynesian macroeconomic model

In this post I will provide a mathematical basis for the multiplier effect which is found when changing an autonomous variable in the aggregate expenditure function (AE). AE is a function which represents the total amount of money that is spent by all consumers in an economy, and is made up of two components: autonomous expenditure (which is exogenous in relation to income) and induced expenditure (endogenous to income). In other words, autonomous expenditure is the y-cut of the AE funtion, and any increases in autonomous expenditure will shift AE vertically. Induced consumption refers to any expenditure that is over and above the level of expenditure at the y-cut, and is directly related to the gradient of the AE function (which includes the marginal propensity to consume¹). Referring to Figure 1 below, let the increase in autonomous expenditure be y₁. y₁ thus shifts AE₁ to AE₂.…

By Aidan Horn| March 15th, 2015|English, Level: intermediate|4 Comments

The domain of a composite function

In this article I outline a systematic way of finding the domain of a composite function. A definition that can be used for this purpose follows:

$D(f \circ g) = \{x|x\in D(g) \wedge g(x) \in D(f)\}$

(Vaught, 1995:18)

Where $D(\lambda) =$ $\text{the domain of }\lambda$

The explanatory method which follows is to show how to use this definition in different examples.

Example 1

Solve $D(\ln(\ln(\ln x)))$ .

Solution:

Let $\ln(\ln(\ln x)) = f(g(h(x)))$

$\begin{minipage}{3in} \begin{align*} \text{Firstly, }& D(g\circ h) = \{x|x\in (0,\infty)\wedge \ln x\in (0,\infty)\} \\ & \ln x\in (0,\infty) \Leftrightarrow x\in (1,\infty) \\ \therefore \; \; & D(g\circ h) = x \in (1, \infty) \\ ~\\ \text{Now, }& D(f \circ (g\circ h)) = \{x|x\in (1,\infty)\wedge \ln(\ln x)\in (0,\infty)\} \\ & \ln(\ln x)\in (0,\infty) \Leftrightarrow \ln x\in (1,\infty) \Leftrightarrow x \in (e,\infty) \\ \therefore \; \; & D(f \circ g\circ h) = x \in (e, \infty) \end{align*} \end{minipage}$

$\square$

Example 2.1

Let $f(x)=x+1$ and $g(x)=x^2$ where $D(g)=[-2,2]$ .

Find $D(f\circ g)$

Solution:

$\begin{minipage}{2in} \begin{align*} f\circ g(x) &= x^2+1 \\ D(f\circ g) &= \{x|x \in [-2,2] \wedge x^2 \in \mathbb{R} \} \\ & x^2 \in \mathbb{R} \Leftrightarrow x \in \mathbb{R} \\ \therefore \; \; & x \in [-2,2] \end{align*} \end{minipage}$

$\square$

Example 2.2

Consider the same constraints as in Example 2.1, but with $D(f)=[-2,1]$

Solution:

$\begin{minipage}{3in} \begin{align*} D(f\circ g) &= \{x|x \in [-2,2] \wedge x^2 \in [-2,1] \} \\ & x^2 \in [-2,1] \Leftrightarrow x^2 \in [0,1] \Leftrightarrow x \in [-1,1] \\ \therefore \;\; & x \in [-1,1] \end{align*} \end{minipage}$

$\square$

References

Vaught, RL. 1995. Set theory: An introduction. 2nd edition. Boston: Birkhäuser.

LaTeX and PDF format here

How clear is this post?

…

By Aidan Horn| March 4th, 2015|English, Level: intermediate|0 Comments