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- Thread starter desmond iking
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ShayanJ

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[itex]

(i-j)\times (i+j)=\underbrace{i\times i}_0+i \times j- j\times i-\underbrace{ j \times j}_0=i\times j+i\times j=2 i \times j=2 k

[/itex]

- #3

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It's wrong before that, even.

[itex]

(i-j)\times (i+j)=\underbrace{i\times i}_0+i \times j- j\times i-\underbrace{ j \times j}_0=i\times j+i\times j=2 i \times j=2 k

[/itex]

##\vec P = P(\vec j -\vec k)/\sqrt 2##

Alternatively, by calculating the distance from A to the line of P the moment is seen to have magnitude ##aP\sqrt {\frac 32}##. I believe the correct answer is exactly half that shown.

- #4

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-j X i=k

That k and the other normal one from i x j=k, add up to 2k.

That k and the other normal one from i x j=k, add up to 2k.

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