Little Joseph once said:

Question

I was once asked to prove that (PROOF ONE) in a right triangle, the sum of the squares of two sides equals the square of the third. Smart little rascal that I am, I proved it with ease. I was then asked to prove that (PROOF 2) if the sum of the squares of two sides of a triangle equals the square of the third side, then that triangle is right. What a stupid question! I'd already proved it once. Why ask me to prove it again? I just wrote down "Already proven."

Comment on Joseph's second proof. Is he as clever as he thinks he is?

Answer 1

Elementary Logic :)

hypothesis - if a cow, then a mammal
if true then

converse - if a mammal then a cow
Not sure
( It is the converse we have here :)

inverse - if not a cow, then not a mammal
Not sure

contrapositive - if not a mammal, then not a cow
True.

Answer 2

aah ok