If $(a_1, b_1, c_1)$ and $(a_2, b_2, c_2)$ are the direction cosines of two lines making an angle $\theta$ with each other,then $\cos \theta =$

  • A
    $a_1 a_2 + b_1 b_2 + c_1 c_2$
  • B
    $|a_1 a_2 + b_1 b_2 + c_1 c_2|$
  • C
    $(a_1 a_2 + b_1 b_2 + c_1 c_2) / (\sqrt{a_1^2 a_2^2 + b_1^2 b_2^2 + c_1^2 c_2^2})$
  • D
    $4/3$

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