Question

5. Two vectors A and B are such that A +B| = |A - B).
The angle between the vectors A and B is
b) 60°
c) 90°
d) 180°
a)0

Answer 1

Answer:

(c)90 degrees

Explanation:

a+b=$\sqrt{a^{2}+b^{2} +2ab cos\alpha }$

a-b = $\sqrt{a^{2}+b^{2} -2ab cos\alpha }$

therefore a+b=a-b

                 on solving

  2ab cos $\alpha$ =-2ab$cos\alpha$

  4ab cos$\\\alpha$ =0

  therafore cos $\alpha$=0

and $\alpha$ = 90degrees

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