[tex]\it a)\ MNPQ-paralelogram \Rightarrow MN||QP\ \ \ \ (1) \\ \\ \\ E\in MN,\ F\in PQ \stackrel{(1)}{\Longrightarrow} ME||QF\ \ \ \ (2)\\ \\ \\ MNPQ-paralelogram \Rightarrow MN= PQ\ \ \ \ (3)\\ \\ \\ E-mijlocul\ lui\ MN,\ F-mijlocul\ lui\ QP\ \stackrel{(3)}{\Longrightarrow} ME=QF\ \ \ \ (4)[/tex]
[tex]\it (2),\ (4) \Rightarrow MEFQ-paralelogram \Rightarrow EF=MQ\\ \\ \\ b)\ MEFQ-paralelogram \Rightarrow EF||MQ\ \ \ \ (5)\\ \\ MNPQ-paralelogram \Rightarrow MQ||NP\ \ \ \ (6)\\ \\ (5),\ (6) \Rightarrow EF||NP[/tex]
