## Articles

Following on from his article 'The prime number lottery' in last issue of Plus, Marcus du Sautoy continues his exploration of the greatest unsolved problem of mathematics: The Riemann Hypothesis.
Human beings are famously prone to error, and proof-readers are, after all, only human. But who picks up the errors a proof-reader misses? John D. Barrow challenges readers to estimate the errors that aren't found from the errors that are.
Calculus is a collection of tools, such as differentiation and integration, for solving problems in mathematics which involve "rates of change" and "areas". In the first of two articles aimed specially at students meeting calculus for the first time, Chris Sangwin tells us about these tools - without doubt, the some of the most important in all of mathematics.
Combinatorial Game Theory is a powerful tool for analysing mathematical games. Lewis Dartnell explains how the technique can be used to analyse games such as Twentyone and Nim, and even some chess endgames.
Marcus du Sautoy begins a two part exploration of the greatest unsolved problem of mathematics: The Riemann Hypothesis. In the first part, we find out how the German mathematician Gauss, aged only 15, discovered the dice that Nature used to chose the primes.
• What is maths for? - What do we hope people will know after studying maths at school?
• New Plus posters! - Find out how you can get hold of your own copy of our brilliant new poster!
• Specially for students - This issue of Plus brings you the first of an occasional series expecially for use in the classroom.
Not only are paper models of geometric shapes beautiful and intriguing, but they also allow us to visualise and understand some important geometric constructions. Konrad Polthier tells us about the gentle art of paper folding.