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AP EAMCET2009MathematicsVector Algebra

Suppose a = i -7 j +3 k , b = i + j +2 k . If the angle between a and b is greater than 90^ , then satisfies the inequality

Options

  1. A-7 < < 1
  2. B>1
  3. C1 < < 7
  4. D-5 < < 1

Correct answer

A. -7 < < 1

Step-by-step solution

Given, a = i -7 j +3 k , b = i + j +2 k array rlrl & = a b | a || b | = ^2-7+6 ^2+49+9 ^2+1+4 ^2 < 0 ( +7)( -1) < 0 -7 < < 1 array

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