Question

Bună, dragilor. Am și eu niște probleme... cine are timp și mă poate ajuta, va rog.

Answer 1

Răspuns:

1.

BD/DC=AB/AC (t.bisect.)

BD+DC=8

BD/DC=6/10=3/5 =>BD=3DC/5

3DC/5 + DC = 8

3DC+5DC=40

8DC=40 =>DC=5 cm =>BD=3 cm

2.

BD/DC=AB/AC (idem)

BD/DC=20/30=2/3 =>BD=2DC/3

2DC/3 + DC = 25

2DC+3DC=75

5DC=75 =>DC=15 cm=>BD=10 cm

tr.CED~tr.CAB =>CD/CB=ED/AB (t.Thales)

15/25=ED/20 =>ED=300/25=12 cm

CE/CA=CD/CB

CE/30=15/25 =>CE=18 cm

P.tr.DEC=18+12+15=45 cm

3.

AD/DC=AB/BC

7/6=21/BC =>BC=18 cm