# A question regarding vectors and angle between vectors

#### raazdeep

In my attempt, I got 2 answers √3 and 1 but the solutions say that the answer is only √3. Am I missing something?  Sent from my S6 using Tapatalk

#### ChipB

PHF Helper
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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#### Pmb

PHF Hall of Fame
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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#### ChipB

PHF Helper
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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