DN=3=>NC=9
**ca sa aflii natura triunghiului BMN trebuie sa ii stii laturile.(si le aflii cu TP)
M mij AD=>AM=MD=6 cm
°AMB,m(MAB)=90°=>MB^2=12^2+6^2
=>MB^2=180=>MB=6√5
°MDN,m(MDN)=90°|=>MN^2=6^2+3^2
=>MD^2=45=>MD=3√5
°BCN,m(BCN)=90°|=>BN^2=9^2+12^2
=>BN^2=225=>BN=15
[tex] (6\sqrt{5} ) ^{2} + (3 \sqrt{5}) ^{2} = 15 ^{2} [/tex]
R.TP
|=> BMN dreptunghic(m(BMN)=90°)
