Question 19
Júlio Daniel has a square sheet of paper with vertices $A,B,C,D$. He first folds it by bringing vertices $B,D$ to the diagonal as shown:
He then brings vertex $C$ to $A$, obtaining a pentagon as shown:
a) Prove that angle $a$ measures $90^\circ$.
b) Determine angle $b$.
He then brings vertex $C$ to $A$, obtaining a pentagon as shown:
a) Prove that angle $a$ measures $90^\circ$.
b) Determine angle $b$.