Răspuns:
notam:
AB=a
AC=b
BC=c
Ptriunghi=3L
a/5=b/12=c/13= k coeficient de proportionalitate
a=5k
b=12k
c=13k
5k+12k+13k=60
30k=60=>k=60:30=>k=2
AB=5×2=>AB=10 cm
AC=12×2=>AC=24 cm
BC=13×2=>BC=26 cm
ca sa demonstam cerinta ΔABC dreptunghic aplicam formula
c=√(a²+b²)
BC=√(10²+24²)=>BC=√(100+576)=>BC=26 (adevarat)
