Notam ABCDA'B'C'D' piramida patrulatera regulata
diagonala bazei mari =√(10²+10²)=10√2
diagonala bazei mici =√(6²+6²)=6√2
ducem inaltimea B'E _I_ AC
EC=(10√2-6√2)/2=2√2 ⇒ AE=10√2-2√2=8√2
in triunghiul AB'E teorema lui Pitagora
B'E=√(AB' ²-AE²)=√[12²-(8√2)²]=√(144-128)=√16=4 cm
