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Clasa a VIII-a geometrie. Ajutor! Problema 2

Clasa A VIIIa Geometrie Ajutor Problema 2 class=

Răspuns :

ducem BE⊥DC, E∈DC ⇒ EC=DC-AB=6
BE=AD=4BC/5
BC^2=(4BC/5)^2 +EC^2 = 16BC^2 / 25 + 36
9BC^2 = 25 x 36
BC=10
AD=8

aria trapez At
At=(DC+AB) x BE/2 = 20 x 8/2
At=80

At= aria BDC+aria ADB = (BC x d)/2 + (AD x AB)/2
80=5 x d + 56/2
d=52/5