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Fie VABCD o piramida patrulatera regulata cu VA⊥VB.Daca VA=10 cm,calculati perimetrul ABCD.

Răspuns :

VAB-echilateral
VA=VB=AB=10cm
VA=VB=VC=VD=10cn
VBC-tr dr is
BC^2=VB^2+VC^2
BC^2=100+100
BC=10-/2
-/ radical
P=20+20-/2
P=20 (1+-/2)cm