## Articles

**Chris Budd**and

**Chris Sangwin**tell us, in 2003 the good old quadratic equation, which we all learned about in school, reached these dizzy pinnacles of fame.

*Plus*, Marcus du Sautoy continues his exploration of the greatest unsolved problem of mathematics: The

**Riemann Hypothesis**.

**paper folding**.

**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.

**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.

*Plus*takes an illustrated tour of an extraordinary geometric construction: the

**Klein bottle**.

**number 23**.

- Plus looks different! - Redesigning the website
- Beauty is truth, truth beauty - The aesthetics of mathematics
- Readers' corner - Rolling with money revisited: The Pyramid Puzzle