Thales is considered the first Greek scientist who showed a scientific mind not dependent on myths and magic. He was the first Greek to turn to mathematics in an abstract mental direction. Thales was born in the city of Miletus and worked in commerce, then in politics, and finally in mathematics, astronomy and philosophy. Among the most important hypotheses attributed to Thales:
1) each circle's diameter can divide it for two halves.
2) The base angles in an isosceles triangle are equal.
3) If two straight lines intersect, then the vertically opposite angles are equal.
4) The sides of two similar triangles are proportional, and Thales used this hypothesis in calculating the height of one of the pyramids.
5) Two triangles are congruent if two angles are equal, and the side included between them from the first triangle is equal to two angles, and the corresponding side from the second triangle. Thales proved these hypotheses and was the first to move geometry from measuring lengths and areas to abstraction.