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JEE Main2012MathematicsVector AlgebraActual

If a+b+c=0,| a |=3,| b |=5 and | c |=7 , then the angle between a and b is

Options

  1. A3
  2. B4
  3. C6
  4. D2

Correct answer

A. 3

Step-by-step solution

Let a+b+c=0 (a+b)=-c (a+b)^2=c^2 aligned & a^2+b^2+2 a b=c^2 & 9+25+2.3 .5 =49 & ( | a |=3,| b |=5 and | c |=7) & = 1 2 = 3 aligned

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