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Fie ABCD un trapez isoscel, AB= 24 cm si CD=9 cm. Daca M pe AD astfel incat DM/AM=3/2, iar MN||AB, N pe BC, calculati lungimea segmentului [MN]

Răspuns :

DM/AM=3/2            
DM/(DM+AM)=DM/AD=3/(2+3)=3/5
MN intersectat cu DB={P}
DM/AD=MP/AB    3/5=MP/24    MP=24*3/5=72/5=14,4

CN/NB=3/2    (CN+NB)/NB=CB/NB=(3+2)/2=5/2    si NB/CB=2/5
NB/CB=NP/CD
2/5=NP/9
NP=2*9/5=18/5=3,6
MN=14/4+3,6=18 cm

Succes!