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# Fp3 vectors watch

1. Why does the cross product of PQ and PR give u the normal vector? Im confused..

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2. (Original post by GPODT)
Why does the cross product of PQ and PR give u the normal vector? Im confused..

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Because PQ and PR both lie in the plane. The only vectors perpendicular to both of them are ones that are perpendicular to the plane.
Hence the cross product gives you a normal vector for the plane.
3. the cross product always generates a vector perpendicular to the crossed vectors. As ghostwalker said since the crossed vectors both lie in the plane the resulting vector must be in the normal direction.
4. (Original post by the bear)
the cross product always generates a vector perpendicular to the crossed vectors. As ghostwalker said since the crossed vectors both lie in the plane the resulting vector must be in the normal direction.
nope
5. (Original post by yaboy)
nope
care to expand ?
6. (Original post by ghostwalker)
Because PQ and PR both lie in the plane. The only vectors perpendicular to both of them are ones that are perpendicular to the plane.
Hence the cross product gives you a normal vector for the plane.
(Original post by the bear)
the cross product always generates a vector perpendicular to the crossed vectors. As ghostwalker said since the crossed vectors both lie in the plane the resulting vector must be in the normal direction.
Cheers!

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Updated: April 19, 2013
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