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31)
Applica il teorema di Pitagora come segue:
$AC= \sqrt{CD^2-AD^2}=\sqrt{29^2-20^2}=21~cm$;
$AB= \sqrt{BC^2-AC^2}=\sqrt{35^2-21^2}=28~cm$;
$DB= AB-AD = 28-20 = 8~cm$;
perimetro del triangolo DBC $2p_{DBC}=CD+DB+BC = 29+8+35 = 72~cm$.
cateto AC = √CD^2-AD^2 = √29^2-20^2 = √841-400 = 21 cm
AB = √BC^2-AC^2 = 7√5^2-3^2 = 7*4 = 28 cm
perimetro ABC = AB+BC+AC = 28+35+21 = 84 cm
perimetro BDC = 29+35+(28-20) = 72 cm
perimetro ACD = 21+20+29 = 70 cm