DC=2 cm
AD=AC-DC=18-2=16 cm
DE║AB⇒
[tex]\frac{CD}{AC} =\frac{CE}{CB} =\frac{DE}{AB} \\\\\\\frac{2}{18} =\frac{CE}{14} =\frac{DE}{12}[/tex]
[tex]CE=\frac{28}{18} =\frac{14}{9} \\\\DE=\frac{24}{18}=\frac{12}{9} \\\\P_{DEC}=2+\frac{26}{9} =\frac{44}{9} \ cm[/tex]
DE║AB⇒
[tex]\frac{DF}{FB} =\frac{EF}{FA} =\frac{DE}{AB} \\\\\frac{EF}{FA} =\frac{DE}{AB}[/tex]
- facem proportie derivata si obtinem
[tex]\frac{AF}{AE} =\frac{AB}{DE+AB} \\\\\frac{AF}{AE}=\frac{12}{\frac{12}{9} +12} \\\\\frac{AF}{AE}=\frac{12}{\frac{120}{9} } =\frac{9}{10}[/tex]
