Triangles

TrianglesDescription
Interior, external and interior opposite angles of trianglesAn explanation is given of what external and internal opposite angles are.  The relationships between the angles of a triangle, and between the external and interior opposite angles are demonstrated and proved.  Besides the conventional proof of the relationship, an additional proof is provided to show the structural relationship between external and interior opposite angles.
Special trianglesExplanations of right angle triangles, isosceles triangles and equilateral triangles.
Congruent trianglesExplains what “congruent” means and what are the conditions that prove that two triangles are congruent to each other.
Pythagorus theoremThe Pythagorus theorem is explained and the truth of the theorem is proved.