## projective geometry

*unless*the lines are parallel. This annoying exception is constantly inserting itself into otherwise simple mathematical statements.

**Burkard Polster**and

**Marty Ross**explain how to get around the problem.

**Runner up in the schools category**. Dusty books, chalky blackboards and checked shirts are all things usually associated with maths. But according to

**Jonathan Tims**, pubs, hot chocolate and cats can be far more inspirational. Join him on a trip through shadow land.

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

**Klein bottle**.

**mathematics of perspective**, researchers are now able to produce three-dimensional reconstructions of the scenes depicted in these works.