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va rog repede , marchez ca cel mai bun!!!!!!

Va Rog Repede Marchez Ca Cel Mai Bun class=

Răspuns :

a)
In∆DBC dr =>T. In. BF²= DF ×FC
AB= EF =20 cm => DE= FB= 20 cm
DF = DE+EF = 20+20=40 cm
BF²= 40×20
BF²= 800
BF=√800
BF=20√2 cm

b)
A= (b+B) ×h/2= (20+60)×20√2/2= 80×20√2/2=40×20√2=800√2 cm²