Fie dreptunghiul ABCD, AB < BC, AB = 10cm, AC = 26 cm
[tex]\it ABC-dreptunghic, m(\hat B)=90^o \stackrel{T.Pitagora}{\Longrightarrow}\ BC^2=AC^2-AB^2 \Rightarrow \\ \\ \Rightarrow BC^2=26^2-10^2=(26-10)(26+10)=16\cdot36=4^2\cdot6^2 \Rightarrow BC=24cm\\ \\ \mathcal{P}=2\cdot(L+\ell)=2(24+10)=2\cdot34=68\ cm[/tex]
