more maths help.............
more maths help.............
SRAW
Rocket Man
2007 Nov 6 • 2525
601 ₧

Show ab + ba is orthogonal to abba . Do not assume 2 or 3 dimensional vectors.
So I tried using the dot product, but I just end up with some magnitude minus another = 0, in which case, I still have no idea what to do...




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2013 Jul 7 at 00:36 UTC



Down Rodeo
Cap'n Moth of the Firehouse
2007 Oct 19 • 5486
57,583 ₧

It's pretty simple, same as the last time you asked. You have an expression for each of the vectors, dot them together. You will find that you have four terms in the expansion because it's the FOIL rule (as you might have been taught). You know, (x + y)(x  y) = x^2 + xy  xy  y^2. It's the antisymmetric one. So you get that, do some simplification, and it could be that it comes out to zero. If you remember that any two vectors whose dot product is zero are orthogonal to each other, well, you've solved it!




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2013 Jul 8 at 23:06 UTC



SRAW
Rocket Man
2007 Nov 6 • 2525
601 ₧

well I didn't know that ab dot ab = a^2 b^2, based on one of the properties of dot product, but thanks anyway!




≡

2013 Jul 9 at 04:22 UTC



Down Rodeo
Cap'n Moth of the Firehouse
2007 Oct 19 • 5486
57,583 ₧

It probably makes sense, geometrically.




≡

2013 Jul 9 at 20:02 UTC



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