See also the Dr. Math FAQ: Browse High School Triangles and
Other Polygons Stars indicate particularly interesting answers
or good places to begin browsing. Selected answers to common
questions: Area of an irregular shape. Pythagorean theorem
proofs. - Proving the Existence of the Centroid [11/16/1999] How
can I prove that the centroid of any arbitrary triangle exists?
- Proving the Pythagorean Theorem: A Traditional and a Modern
Approach [01/27/1998] Can you please explain how I can prove the
Pythagorean theorem? - Proving the Pythagorean Theorem in Two
Steps [1/28/1996] I was trying to prove the Pythagorean theorem
for a friend of mine, and eventually we figured it out. But then
he said that he had heard of a "proof in only six easy steps."
Do you know anything of this? - Proving the Pythagorean Theorem
using Congruent Squares [12/5/1995] A friend of mine is irked
because of constant use of the Pythagorean theorem, which he has
not seen proven. - Proving Trapezoid Congruency [12/19/2001]
Prove that the side