Capítulo 6 · Neste capítulo você vai

Perpendicularity

  • define perpendicular lines and prove that the perpendicular exists and is unique;
  • recognize height and perpendicular bisector;
  • use projections to compare oblique segments;
  • calculate distances and use the properties of perpendicular bisector and angle bisector.

The right angle is at the intersection of streets, at the corner of walls and at the corners of a sheet of paper. In this chapter it gains a precise definition — without measuring anything — and a family of consequences.

Perpendicular streets: four right angles at the intersection.
Perpendicular streets: four right angles at the intersection.
The Egyptians used right angles to align pyramids and temples.
The Egyptians used right angles to align pyramids and temples.
Babylonians also used perpendicularity in constructions and measurements.
Babylonians also used perpendicularity in constructions and measurements.