DE=FC=(21-11):2
DE=FC=10:2
DE=FC= 5 cm
In triunghiul BDF: m (A)=90 grade, aplicăm T.P.
BD^2=BF^3+DF^2
20^3=BF^2+16^2
400=BF^3+256
BF^2=400-256
BF^2=144
BF= radical din 144
BF=12cm (inaltimea)
In triunghiul BCF:m (F)=90grade, aplicăm T.P.
BC^2=BF^2+CF^2
BC^2=12^2+5^2
BC^2=144+25
BC^2=169
BC= radical din 169
BC=13 cm
BC=AD=13 cm
P triunghiului=AB+BC+CD+AC
=21+13+11+13=
=58 cm
Sper ca te-am ajutat
