If $\theta$ is the angle between two vectors $\vec{a}$ and $\vec{b}$ such that $|\vec{a}|=7$, $|\vec{b}|=1$ and $|\vec{a} \times \vec{b}|^2 = k^2 - (\vec{a} \cdot \vec{b})^2$, then the values of $k$ and $\theta$ are

  • A
    $k=1, \theta=45^{\circ}$
  • B
    $k=7, \theta=60^{\circ}$
  • C
    $k=49, \theta=90^{\circ}$
  • D
    $k=7$ and $\theta$ is arbitrary

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