MN=√(12^2+16)=4√10 cm (pitagora in MBN)
MD=√(18^2+36)=6√10 cm (pitagora in DAM)
DN=√(18^2+14^2)=2√130 cm (pitagora in NCD)
aria MND=aria ABCD - aria DAM - aria MBN - aria NCD
aria MND=18^2 - 3x18 - 24 - 7x18
aria MDN=120 cm2
aria MND=MNxNDxDM/4R (aria triunghiului in functie de laturi si raza cercului circumscris)
R=MNxNDxDM/4A=240x2√130/4x120=√130 cm
