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Vector Algebra

Question
CBSEENMA12034070

If open vertical bar straight a with rightwards arrow on top close vertical bar space equals space square root of 3 comma space space open vertical bar straight b with rightwards arrow on top close vertical bar space equals space 2 space and space straight a with rightwards arrow on top. space straight b with rightwards arrow on top space equals space 3 comma find the angle between straight a with rightwards arrow on top space and space straight b with rightwards arrow on top.

Solution
open vertical bar straight a with rightwards arrow on top close vertical bar space equals space square root of 3 comma space space space open vertical bar straight b with rightwards arrow on top close vertical bar space equals space 2 comma space space straight a with rightwards arrow on top. space straight b with rightwards arrow on top space space equals 3
  Let straight theta be angle between straight a with rightwards arrow on top space and space straight b with rightwards arrow on top
  Now,         straight a with rightwards arrow on top. space space straight b with rightwards arrow on top space equals space 3 space space space space space space space rightwards double arrow space space space space open vertical bar straight a with rightwards arrow on top close vertical bar space open vertical bar straight b with rightwards arrow on top close vertical bar space cos space straight theta space equals space 3
therefore space space space left parenthesis square root of 3 right parenthesis thin space left parenthesis 2 right parenthesis space cos space straight theta space equals space 3 space space space space space space rightwards double arrow space space space cos space straight theta space equals fraction numerator square root of 3 over denominator 2 end fraction
therefore space space space space space space space straight theta space equals space 30 degree