Va rog repede dau coroana daca e bine

ABCD- patrat
AC, BD- diagonale
AC ∩ BD
=> AC _|_ BD=> m(< COD)=90 °
ΔDEC- dreptunghic isoscel => DE=EC ; m(< DEC)= 90°
DOCE- patrulater
m(<COD)=m(<DEC)= 90°
DE=EC