I need some help with the the following problem:

If vectors a and b are orthogonal, |a|=3, |b|=4.

Calculate:

a) p=|(a+b)x(a-b)|

b) q=|(3a-b)x(a-2b)|

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- Feb 10th 2009, 01:17 PMsillymeproblem with vectors
I need some help with the the following problem:

If vectors a and b are orthogonal, |a|=3, |b|=4.

Calculate:

a) p=|(a+b)x(a-b)|

b) q=|(3a-b)x(a-2b)| - Feb 10th 2009, 01:50 PMPlato
- Feb 10th 2009, 02:12 PMsillyme
- Feb 10th 2009, 02:26 PMo_O
Some useful properties:

So:

But since they're orthogonal .... - Feb 10th 2009, 02:37 PMsillyme
Thank you o_O.

- Feb 11th 2009, 06:56 AMHallsofIvy
A very simple way to do this is to set up a coordinate system so the and .

Then , , , and .