Posted in Humor

Definitions of Commonly Used Words in Math Lectures

It’s time to review some terms you hear in math lectures. If you are not doing well in math, it’s probably because of miscommunications and not for any other reason.

BRIEFLY: I’m running out of time, so I’ll just write and talk faster.

BRUTE FORCE: Four special cases, three counting arguments, two long inductions, and a partridge in a pair tree.

BY A PREVIOUS THEOREM: I don’t remember how it goes (come to think of it, I’m not really sure we did this at all), but if I stated it right, then the rest of this follows.

CANONICAL FORM: 4 out of 5 mathematicians surveyed recommended this as the final form for the answer.

CHECK FOR YOURSELF: This is the boring part of the proof, so you can do it on your own time.

CLEARLY: I don’t want to write down all the in-between steps.

ELEGANT PROOF: Requires no previous knowledge of the subject, and is less than ten lines long.

FINALLY: Only ten more steps to go…

HINT: The hardest of several possible ways to do a proof.

IT IS WELL KNOWN: See “Mathematische Zeitschrift”, vol XXXVI, 1892.

LET’S TALK THROUGH IT: I don’t want to write it on the board because I’ll make a mistake.

OBVIOUSLY: I hope you weren’t sleeping when we discussed this earlier, because I refuse to repeat it.

ONE MAY SHOW: One did, his name was Gauss.

PROCEED FORMALLY: Manipulate symbols by the rules without any hint of their true meaning.

PROOF OMITTED: Trust me, it’s true.

Q.E.D. : T.G.I.F.

QUANTIFY: I can’t find anything wrong with your proof except that it won’t work if x is 0.

RECALL: I shouldn’t have to tell you this, but for those of you who erase your memory after every test, here it is again.

SIMILARLY: At least one line of the proof of this case is the same as before.

SKETCH OF A PROOF: I couldn’t verify the details, so I’ll break it down into parts I couldn’t prove.

SOFT PROOF: One third less filling (of the page) than your regular proof, but it requires two extra years of course work just to understand the terms.

THE FOLLOWING ARE EQUIVALENT: If I say this it means that, and if I say that it means the other thing, and if I say the other thing…

TRIVIAL: If I have to show you how to do this, you’re in the wrong class.

TWO LINE PROOF: I’ll leave out everything but the conclusion.

WITHOUT LOSS OF GENERALITY (WLOG): I’m not about to do all the possible cases, so I’ll do one and let you figure out the rest.

Please use the comment form to share your own commonly used words in your math lectures.

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Posted in Geometry

A problem solving lesson about triangles and circles

This short lesson was inspired by one of the problems from the blog Five  Triangles Mathematics. The author challenges the reader to construct a circle using only a compass and straight edge, through two points X and Y. The centre of the circle must be a point on the line located between the two given points. If you can’t visualise it, click here to see the diagram and try the problem first and then come back if you are interested to see how you might teach this in your class without losing the essence of the problem solving activity.

Here’s my sequence of tasks. Notice that all three tasks involve geometric constructions in increasing complexity, one building on the previous task.

Problem 1

You can use this as context for reviewing the properties of isosceles triangle after the students have come up with at least two solutions.

Problem 2

Solution

This is one of the solution but I suggest you ask students to come up with other ways of constructing the isosceles triangle. The procedure shown involved constructing the perpendicular bisector of CD. F is any point on the perpendicular bisector.

Problem 3

locating the center of circle

Solution

(Of course I hid some part of the construction to make it a little bit of a challenge. Do you think the location of J is unique?)

In terms of time, this is not actually a short lesson because you need to give students more time to solve the problems. You may also want to read How to scaffold problem solving in geometry. The following book is a good resource for tasks that fosters geometric thinking.

Posted in Math videos

The problem with physics education is math education

I hope these two videos will make us think hard as well about the problems in mathematics education and how important it is to teach math in a way that they makes sense to students. Students are only able to apply their maths to the extent that they understand them.

Bring the mathematics back to physics!

This second video is an open letter to Mr. President Barack Obama. It presents a problem about Physics Education. The problem is as true in mathematics although I think for both physics and math, the problem is not just the curriculum but also in the teaching.

Posted in What is mathematics

What is good mathematics?


Terence Tao

It may not be for the majority of learners but it remains an important goal of math education in the basic level to hone future mathematicians who in turn are expected to produce good mathematics.  This post presents Terence Tao‘s personal thoughts on what good quality mathematics could mean. Terence was a child prodigy. When he was 24, he was promoted to full professor at UCLA and remains the youngest person ever appointed to that rank by the institution. Terence Tao currently holds the James and Carol Collins chair in mathematics at the University of California, Los Angeles. He was one of the recipients of the 2006 Fields Medal.

What I like about Terence’ descriptions of good quality mathematics is that it is possible at K-12 levels for students to actually produce good mathematics within the universe of their knowledge given the right motivation and challenge, the appropriate activity, enough opportunity, etc. I think students have the right to participate in the production of mathematical knowledge. Activities such as problem solving, mathematical investigations, and  modelling are all about training students to “produce” good mathematics.

Good mathematics could refer to any of the following:
  1. Good mathematical problem-solving (e.g. a major breakthrough on an important mathematical problem);
  2. Good mathematical technique (e.g. a masterful use of existing methods, or the development of new tools);
  3. Good mathematical theory (e.g. a conceptual framework or choice of notation which systematically unifies and generalises an existing body of results);
  4. Good mathematical insight (e.g. a major conceptual simplification, or the realisation of a unifying principle, heuristic, analogy, or theme);
  5. Good mathematical discovery (e.g. the revelation of an unexpected and intriguing new mathematical phenomenon, connection, or counterexample);
  6. Good mathematical application (e.g. to important problems in physics, engineering, computer science, statistics, etc., or from one field of mathematics to another);
  7. Good mathematical exposition (e.g. a detailed and informative survey on a timely mathematical topic, or a clear and well-motivated argument);
  8. Good mathematical pedagogy (e.g. a lecture or writing style which enables others to learn and do mathematics more effectively, or contributions to math- ematical education);
  9. Good mathematical vision (e.g. a long-range and fruitful program or set of conjectures);
  10. Good mathematical taste (e.g. a research goal which is inherently interesting and impacts important topics, themes, or questions);
  11. Good mathematical public relations (e.g. an effective showcasing of a mathematical achievement to non-mathematicians, or from one field of mathematics to another);
  12. Good meta-mathematics (e.g. advances in the foundations, philosophy, history, scholarship, or practice of mathematics);
  13. Rigorous mathematics (with all details correctly and carefully given in full);
  14. Beautiful mathematics (e.g. the amazing identities of Ramanujan; results which are easy (and pretty) to state but not to prove);
  15. Elegant mathematics (e.g. Paul Erdos’ concept of “proofs from the Book”; achieving a difficult result with a minimum of effort);
  16. Creative mathematics (e.g. a radically new and original technique, viewpoint, or species of result);
  17. Useful mathematics (e.g. a lemma or method which will be used repeatedly in future work on the subject);
  18. Strong mathematics (e.g. a sharp result that matches the known counterexamples, or a result which deduces an unexpectedly strong conclusion from a seemingly weak hypothesis);
  19. Deep mathematics (e.g. a result which is manifestly non-trivial, for instance by capturing a subtle phenomenon beyond the reach of more elementary tools); Intuitive mathematics (e.g. an argument which is natural and easily visualisable);
  20. Definitive mathematics (e.g. a classification of all objects of a certain type; the final word on a mathematical topic);

You can find the link to the complete paper in Terence Tao’s WordPress blog. You may also want to read Terence’s books.