Possible Clues:

• Greek mathematician
• Greek philosopher and mathematician
• Mathematician with a theorem about right triangles
• Mathematician's graph, say, to change
• Ay to graphs (anag) - 21 3 17 theorist
• Ancient mathematician
• Philosopher retraces Argosy path
• His argument's well known to be three-sided
• Mathematician makes amendment to graph, say
• Gosh, a party was thrown for old mathematician