If you mean a2+b2 = c2 then it's Pythagoras' theorem
A ruler or a compass would help or aternatively use Pythagoras' theorem to prove that the diagonals are of equal lengths
Yes, the corollary to one theorem can be used to prove another theorem.
Yes, he must have proved his own Theorem otherwise it would not have been adopted by mathematicians across the globe. I'm sure you could test out the theorem: check whether c2 really does equal b2 + a2 in a manual measurement of a triangle; though this is less accurate and not as precise as the Theorem.
Theorem 8.11 in what book?
You cannot solve a theorem: you can prove the theorem or you can solve a question based on the remainder theorem.
Pythagoras was a teacher, but he also was the first to prove Pythagorean math correct
asa theorem
A theorem to prove. A series of logical statements. A series of reasons for the statements. answer theorem to prove
A segment need not be a bisector. No theorem can be used to prove something that may not be true!
HL congruence theorem
I will give a link that explains and proves the theorem.