- 



SCIENCE AUSOLTTK or Si&amp;gt; UK. 







7. If BX and CPare each II AM, and C 

 not on tin- straight BN; also BN II CP. 

 Kcrthe rays BX and CP do not in- 

 tersecl &amp;lt;^&quot;&amp;gt;: but AM, BN and CP 

 either are or are not in the same 

 plain-: and in the first case, AM either 

 i- or is not within BNCP. 

 i i. :.. If AM, BN, CP are complanar, and 

 AM falls within BNCP; then every ray PO 

 (in NBC) ruts the ray AM in some point D 

 (since BNHAM): moreover, since DMilCP 

 ( (}}. the ray DO will rut the ray CP, and so 

 BN II CP. 



P&amp;gt;ut if BN and CP are on the same side of 

 AM: then one of them, for example 

 CP, falls between the two other 

 straights BN, AM: but every ray BQ 

 (in NBA) ruts the ray AM, and so 

 also the straight CP. Therefore 

 BN II CP. 



i&quot; If the planes MAB, MAC make 



an angh . then CPX and ABN have in com 

 mon nothing but the ray PX, while the ray 

 AM (in APXi and the ray BN, and SO also 

 XPC and the ray AM have nothing in com 

 mon. 



Put hemi-plane PCD. drawn through any 

 raj PD (in XPA), ruts the ray AM. Since ray 





B C 



