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Old Nov 8th 2018, 12:06 AM   #1
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A question regarding vectors and angle between vectors

In my attempt, I got 2 answers √3 and 1 but the solutions say that the answer is only √3. Am I missing something?

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Old Nov 9th 2018, 04:45 AM   #2
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Consider the first equation you are given:

$ | \hat A \times \hat B | = - \sqrt 3 \ \hat A \cdot \hat B $

The left hand side is a positive number, since it's a magnitude. Therefore the right hand side must also be positive, which means $ \hat A \cdot \hat B$ must be negative. This rules out the possibility that theta = -60 degrees.
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Old Nov 11th 2018, 01:30 PM   #3
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Originally Posted by ChipB View Post
Consider the first equation you are given:

$ | \hat A \times \hat B | = - \sqrt 3 \ \hat A \cdot \hat B $
That expression is not in the paper he posted. The cross product is defined for two vectors whose magnitude does not appear explicitly in the expression defining it;.
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Old Nov 11th 2018, 02:59 PM   #4
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Originally Posted by Pmb View Post
That expression is not in the paper he posted.
?? It’s the very first line of the photo the OP posted from his text with the problem statement - are you not seeing it?
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Last edited by ChipB; Nov 11th 2018 at 03:02 PM.
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