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Lato $\small AB= 10\,cm;$
diagonale maggiore $\small BD = 16\,cm;$
diagonale minore $\small AC= \dfrac{1}{2}·BD = \dfrac{1}{\cancel2_1}×\cancel{16}^8 = 8\,cm;$
perimetro $\small 2p= 4·AB = 4×10 = 40\,cm.$