**NicolĂ˛ Fontana Tartaglia**(ca. 1499-1557)- Born in Italy.
- His work in algebra led to the first generalized solution of cubic equations.
- He made contributions to fundamental arithmetic, ballistics, military engineering, and survey instruments.

**Thales**(ca. 625 BCE – ca. 547 BCE)- Born in Turkey.
- Tradition states that he was the first to prove these geometric results:
- (1) vertical angles are equal;
- (2) the angle sum of a triangle equals two right angles;
- (3) the base angles of an isosceles triangle are equal;
- (4) an angle inscribed in a semi-circle is a right angle.

**Theaetetus**(417 BCE – 369 BCE)- Born in Greece.
- He developed the theory of incommensurable magnitudes.