Răspuns:
1.ΔADC-dreptunghic in ∠A=90°⇒TP:ip²=c1²⁺c2²
AC²=AD²⁺DC²²
13²=AD²⁺5²
AD²=169-25
AD²=√144√√√
AD=144
AD=12 cm
2.ΔAED , ∡A=90°
AD²=AE²⁺DE²
10²=AE²⁺(2√5)²
100=AE²⁺20
AE²=100-20
AE=80
AE=√80
AE=4√5
3.ΔDEF , ∡D=90°
DE=3 cm
DF=4 cm
EF=?
EF²=DE²⁺DF²
EF²=3²⁺4²
EF²=9⁺16
EF²=15
EF=√15.
SUCCES!
