Maths - Projections of lines on lines

Maths - Projections of lines on lines - Forum discussion

By: Nobody/Anonymous - nobody
Error projecting line onto perpendicular
2004-09-27 18:36

On this page:
http://www.euclideanspace.com/maths/geometry/elements/line/projections/index.htm

You state that the formula to find the perpendicular component (when projecting one vector against another) is:
A _|_ B = (A x B /|B|) x B /|B|

While I'm too lazy to look at the math, my experimentation shows that this is incorrect. The correct formula should be:

A _|_ B = (-A x B / |B| ) x B / |B|

(When using the original formula, the resulting vector is pointing in the wrong direction, and needs to be swapped to point in the correct direction.)

By: Martin Baker - martinbaker
RE: Error projecting line onto perpendicular
2004-09-29 08:52

Thanks very much, I think you are right.

I have corrected the page and added an example at the end to confirm this is correct.

I have not yet checked the matrix and clifford parts.

Martin

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