Curated OER
Ceva’s Theorem
Students prove and use Ceva's Theorem to solve problems. In this geometry lesson, students analyze polygons for patterns and calculate the area of each shape. They relate polygons to the real world.
Cut the Knot
Cut the Knot: Existence of the Orthocenter
This site defines the altitude of a triangle and gives the standard notation for altitudes of a triangle. The site then goes to list several proofs involving altitudes and orthocenters.