IIT-JEE 2004Question 401
$P_1$ and $P_2$ are planes passing through the origin. $L_1$ and $L_2$ are two lines on $P_1$ and $P_2$ respectively such that their intersection is the origin. Show that there exist points $A,B,C$, whose permutation $A',B',C'$ can be chosen such that (i) $A$ is on $L_1$, $B$ on $P_1$ but not on $L_1$ and $C$ not on $P_1$; (ii) $A'$ is on $L_2$, $B'$ on $P_2$ but not on $L_2$ and $C'$ not on $P_2$.
3D Geometry
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