The direction cosine of the vector $\vec{a} = 3\hat{i} + 4\hat{j} + 5\hat{k}$ in the direction of the positive $x$-axis is:

  • A
    $\pm \frac{3}{\sqrt{50}}$
  • B
    $\frac{4}{\sqrt{50}}$
  • C
    $\frac{3}{\sqrt{50}}$
  • D
    $-\frac{4}{\sqrt{50}}$

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