2022 ACJC Promo Q10

2022 ACJC Promo Q10

10 marks
Promo

The plane \({{P}_{1}}\) has the equation \(-6x-4y+2z=4\).

  1. Find the vector equations of the planes such that the perpendicular distance from each plane to \({{P}_{1}}\) is \(10\) units.[2]

The plane \({{P}_{2}}\) has the equation \(-x-y+2z=k\), where \(k\) is a constant.

  1. Find the angle between \({{P}_{1}}\) and \({{P}_{2}}\).[2]
  2. The planes \({{P}_{1}}\) and \({{P}_{2}}\) intersect in the line \(L\). Show that a possible vector equation of \(L\) is \(\mathbf{r}=\left( \begin{matrix} 2k-2 \\ 2-3k \\ 0 \\ \end{matrix} \right)+\lambda \left( \begin{matrix} -3 \\ 5 \\ 1 \\ \end{matrix} \right)\), \(\lambda \in \mathbb{R}\).[3]

The plane \({{P}_{3}}\) has the equation \(5x+\beta y+5z=\mu \), where \(\beta \), \(\mu \in \mathbb{R}\).

  1. Given that the line \(L\) is contained in the plane \({{P}_{3}}\), find \(\beta \) and \(\mu \), giving your answer in terms of \(k\) if necessary.[2]
  2. Given instead that the line \(L\) does not intersect \({{P}_{3}}\), what can be said about the values of \(\beta \) and \(\mu \)?[1]

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Answer:(i) \(\mathbf{r} \cdot \begin{pmatrix} -3 \\ -2 \\ 1 \end{pmatrix} = 2 \pm 10\sqrt{14}\) (ii) \(40.2°\) (iii) \(L: \mathbf{r} = \begin{pmatrix} 2k-2 \\ 2-3k \\ 0 \end{pmatrix} + \lambda \begin{pmatrix} -3 \\ 5 \\ 1 \end{pmatrix}\) (iv) \(\mu = 4k - 6\) (v) \(\beta = 2\), \(\mu \ eq 4k - 6\)

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