User talk:Rtgjr

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Hello,, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are some pages that you might find helpful: I hope you enjoy editing here and being a Wikipedian! Please sign your messages on discussion pages using four tildes ( ~ ); this will automatically insert your username and the date. If you need help, check out Questions, ask me on, or ask your question on this page and then place  before the question. Again, welcome! RJFJR (talk) 21:14, 26 December 2009 (UTC)
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Plane (geometry)
Regarding your post to the maths Wiki-project. The article is correct. Think of the plane z = 1 in xyz-space. This plane passes through r0 = (0,0,1) and contains the vectors v = (1,0,0) and w = (0,1,0). So r0 + sv + tw = (0,0,1) + s(1,0,0) + t(0,1,0) = (s,t,1) which does indeed parametrise the plane z = 1. If we compute your expression, we have r0 + s(v &minus; r0) + t(w &minus; r0) = (0,0,1) + s(1,0,&minus;1) + t(0,1,&minus;1) = (s,t,1 &minus; s &minus; t). This last expression does not parametrise the plane z = 1; for example, when s = t = 0 we have the point (1,1,&minus;1), which is not a point on the plane z = 1. Dr Dec (Talk)  21:51, 26 December 2009 (UTC)
 * What his expression actually describes is a plane passing trough the points r0, v and w, whereas the original is a plane passing trough r0 and containing the directions v and w.--LutzL (talk) 16:25, 30 December 2009 (UTC)