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Topic: repost:: geometry question
Replies: 0

 Bob Peeples Posts: 2 Registered: 12/12/04
repost:: geometry question
Posted: Jul 11, 1996 1:34 AM

In three-space, 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 126ÃÂÃÂº and 234ÃÂÃÂº from the +X
axis. A third is along the +X axis at some angle above the XY plane. It
is 120ÃÂÃÂº 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) 120ÃÂÃÂº / \ 120ÃÂÃÂº (hexagon portion)
/ / 108ÃÂÃÂº (pentagon
portion)
Assume pentagon lies in XY plane.