Tag Archives: intermediate

Combinatorial Game Theory VI

Lesson 6 General Combinatorial Game Theory [ Warning: the following lesson is significantly longer than the previous ones. ] Starting from this lesson, we will look at a more rigourous, complete and general theory. Prior to this, in any game configuration both … Continue reading

Posted in Notes | Tagged , , , , , , , , | Leave a comment

Thinking Infinitesimally – Multivariate Calculus (I)

[ Background required: some understanding of single-variable calculus, including differentiation and integration. ] The object of this series of articles is to provide a rather different point-of-view to multivariate calculus, compared to the conventional approach in calculus texts. The typical … Continue reading

Posted in Notes | Tagged , , , , | Leave a comment

Power Series and Generating Functions (IV) – Exponential Generating Functions

Note: this article is noticeably more difficult than the previous instalments. The reader is advised to be completely comfortable with generating functions before proceeding. We’ve already seen how generating functions can be used to solve some combinatorial problems. The nice … Continue reading

Posted in Notes | Tagged , , , , , | 3 Comments

Power Series and Generating Functions (III) – Partitions

One particularly fruitful application of generating functions is in partition numbers. Let n be a positive integer. A partition of n is an expression of n as a sum of positive integers, where two expressions are identical if they can be obtained from each … Continue reading

Posted in Notes | Tagged , , , , , , | Leave a comment

Power Series and Generating Functions (II): Formal Power Series

For today’s post, we shall first talk about the Catalan numbers. The question we seek to answer is the following. Let n be a positive integer. Given a non-associative operation *, find the number of ways to bracket the expression … Continue reading

Posted in Notes | Tagged , , , , | Leave a comment

Power Series and Generating Functions (I): Basics

[ Background required: basic combinatorics, including combinations and permutations. Thus, you should know the formulae and and what they mean. Also, some examples / problems may require calculus. ] Note: this post is still highly relevant to competition-mathematics. 🙂 To … Continue reading

Posted in Notes | Tagged , , , , , | Leave a comment

What is Curvature? (II)

[ Background required: rudimentary vector calculus. ] The aforementioned definition of curvature is practical but a little aesthetically displeasing. Specifically, one seeks a definition which is independent of the parametrization of the curve. The advantage of such a definition is … Continue reading

Posted in Extra | Tagged , , | 1 Comment

Pick’s Theorem and Some Interesting Applications

[ Background required: none. ] A lattice point on the cartesian plane is a point where both coordinates are integers. Let P be a polygon on the cartesian plane such that every vertex is a lattice point (we call it a lattice polygon). … Continue reading

Posted in Extra | Tagged , , , , , , | 1 Comment

Linear Algebra: Inner Products

[ Background required: basic knowledge of linear algebra, e.g. the previous post. Updated on 6 Dec 2011: added graphs in Application 2, courtesy of wolframalpha.] Those of you who already know inner products may roll your eyes at this point, … Continue reading

Posted in Notes | Tagged , , , , , , , | Leave a comment

Quadratic Residues – Part IV (Applications)

Let p be an odd prime and g be a primitive root modulo p. Given any a which is not a multiple of p, we can write for some r. We mentioned at the end of the last section that a is a square if … Continue reading

Posted in Notes | Tagged , , , | 3 Comments