If `P_1:vec r.vecn_1-d_1=0` `P_2:vec r.vec n_2-d_2=0` and `P_3:vec r.vecn_3-d_3=0` are three non-coplanar vectors, then three lines `P_1= 0`, `P_2=0`; `P_2=0`,`P_3=0` ; `P_3=0` `P_1=0` are