Răspuns:
Fie AB=L, AD=l. Atunci
[tex]\displaystyle A_{BEF}=A_{ABCD}-A_{ABE}-A_{BCF}-A_{EFD}=\\=L\cdot l-\frac{L\cdot\frac{l}{2}}{2}-\frac{\frac{L}{2}\cdot l}{2}-\frac{\frac{L}{2}\cdot\frac{l}{2}}{2}=\\=\frac{3}{8}L\cdot l=\frac{3}{8}A_{ABCD}\Rightarrow\displaystyle\frac{A_{BEF}}{A_{ABCD}}=\frac{3}{8}[/tex]
Explicație pas cu pas:
