This unit deals with some formulae connected to Thales' theorem. Rather than giving rigorous, step-by-step demonstrations, this unit offers the advantage of verifying conclusions and properties in a straightforward manner. To conclude, different examples of similarity in triangles and polygons in general is also focused on, through an interactive approach.

There is an introduction to metric relations in a right-angled triangle: the theorem of the sides adjacent to the right angle and the perpendicular height theorem.

• Apply Thales' theorem to cases where segments are in proportion to each other.

• Construct similar polygons and work out their related measurements.

• Understand and know how to apply the theorem of the sides adjacent to the right angle and the perpendicular height theorem.