Multiple choice

If $\bar{a}$and $\bar{b}$ are two arbitrary vectors with magnitudes a and b respectively, $|\bar{a} \times \bar{b}|^2$will be equal to

  1. $a^2b^2 - (\bar{a}.\bar{b})^2$
  2. $ab - \bar {a}.\bar{b}$
  3. $a^2b^2 + (\bar{a}.\bar{b})^2$
  4. $ab + \bar {a}.\bar{b}$
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A Correct answer
Explanation

Lagrange's identity states that |a x b|^2 = |a|^2 |b|^2 - (a . b)^2. This is a standard vector identity.

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