Could you please teach me how to solve this question? I don't know how to do it at all. Thank you very much. Question: Prove: If a , b, c, and d lie in the same plane when positioned with a common initial point then (a*b) * (c *d) =0.

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Originally Posted by Jenny20 Could you please teach me how to solve this question? I don't know how to do it at all. Thank you very much. Question: Prove: If a , b, c, and d lie in the same plane when positioned with a common initial point then (a*b) * (c *d) =0. is a vector normal to the plane containg and . Similarly is a vector normal to the plane containg and . But these two planes are the same plane so and are parallel (or anti-parallel) and hence: RonL

Last edited by CaptainBlack; Jan 2nd 2007 at 02:31 PM.