Euclid

Euclid lived around 300 BC and taught mathematics at Alexandria under Ptolemy I. Of his life almost nothing is known beyond a single anecdote: when the king asked whether there was a shorter way to learn geometry, he replied, 'There is no royal road to geometry.' His Elements gathered the achievements of earlier Greek mathematics into a rigorous system that proceeds step by step from definitions, postulates and axioms, and for more than two thousand years it was the most important textbook in the world.