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repost:: geometry question
Posted:
Jul 11, 1996 1:34 AM


In threespace, if the angles between three unit vectors from the origin are known and the first two unit vectors are determined, how can I determine the third vector? This is a repost of my soccer ball (truncated icosahedron) question from a few days ago. I calculated the angles incorrectly in the previous post. Perhaps that is why it stumped everyone.
The first two vectors are in the XY plane at 126ÃÂÃÂº and 234ÃÂÃÂº from the +X axis. A third is along the +X axis at some angle above the XY plane. It is 120ÃÂÃÂº from either of the other vectors. What is the angle above the XY plane of the third vector?
^  define third unit vector?  +X   (hexagon portion) 120ÃÂÃÂº / \ 120ÃÂÃÂº (hexagon portion) / / 108ÃÂÃÂº (pentagon portion) Assume pentagon lies in XY plane.



