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3-1.Vectors
medium
$(\mathop A\limits^ \to + \mathop B\limits^ \to )\, \times (\mathop A\limits^ \to - \mathop B\limits^ \to )$ का मान है
A
$0$
B
${A^2} - {B^2}$
C
$\mathop B\limits^ \to \times \mathop A\limits^ \to $
D
$2(\mathop B\limits^ \to \times \mathop A\limits^ \to )$
Solution
(d)$(\vec A + \vec B) \times (\vec A – \vec B)$
$ = \vec A \times \vec A – \vec A \times \vec B + \vec B \times \vec A – \vec B \times \vec B$
$ = 0 – \vec A \times \vec B + \vec B \times \vec A – 0$
$ = \vec B \times \vec A + \vec B \times \vec A = 2(\vec B \times \vec A)$
Standard 11
Physics