ban chiu kho tu ve hinh nhe!a,
Trong mp$(ABN)$: $ME\cap BN=J\Rightarrow \left\{ \begin{array}{l} J\in ME\\ J\in BN\subset (BCD) \end{array} \right.\Rightarrow J=ME\in (BCD)$
b,
$*$ta co $Q\in (EMQ)\cap ( BCD) (1)$
Trong mp $(BCD):CD\cap QJ=P\Rightarrow P\in (EMQ)\cap (BCD) (2)$
Tu $(1)$ va $(2)$$:(EMQ)\cap (BCD)=PQ$
$*M\in (EMQ)\cap (ABD) $
Trong mp$(ACD):EP\cap AD=F\Rightarrow F\in (EMQ)\cap (ABD)$
$\Rightarrow (EMQ)\cap (ABD)=FM$
c,
Ta co:$\left\{ \begin{array}{l} (QME)\cap (ABC)=QM\\(QME)\cap (BCD)=QP\\(QME)\cap(ACD)=FP\\ (QME)\cap(ABD)=MF \end{array} \right.$
Vay thiet dien cat boi mp$(QME)$la tu giac $FMQP$