120
lDBl^2= lABl^2+lADl^2
17^2= lABl^2+ 8^2
289= lABl^2+ 64
lABl^2= 289-64
lABl^2= 225
lABl= 15 cm olur.
Dikdörtgen in alanı;
A= lABl.lADl= 15.8= 120 cm^2 olur.