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#1

$Old$ October 21st, 2009, 04:54 PM

GemGems123 $GemGems123 is offline$

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$Default$ Vector Geometry Question!

Hi, im really stuck on this question so would be very grateful if someone could help me with it!

Thanks
Gemma

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$Old$ October 22nd, 2009, 01:11 AM

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Originally Posted by GemGems123 $View Post$

Hi, im really stuck on this question so would be very grateful if someone could help me with it!

Thanks
Gemma

To get rid of the absolute values square both sides of the given equation:

$|\vec a + \vec b| = |\vec a - \vec b|~\implies~(\vec a + \vec b)^2 = (\vec a - \vec b)^2$

$(\vec a)^2+2\cdot \vec a \cdot \vec b +(\vec b)^2=(\vec a)^2-2\cdot \vec a \cdot \vec b +(\vec b)^2~\implies~2\cdot \vec a \cdot \vec b = -2\cdot \vec a \cdot \vec b~\implies~4\cdot \vec a \cdot \vec b = 0$

I'll leave the rest for you.

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