2022 RI P2 Q3

2022 RI P2 Q3

12 marks
Prelims

The line \({{L}_{1}}\) has equation \(1-y=\frac{z-1}{2}\), \(x=2\), and meets the \(xy\)-plane at point \(P\). The point \(A\) has position vector \(\left( \begin{matrix} 3 \\ -1 \\ 2 \\ \end{matrix} \right)\) with reference to the origin \(O\).

  1. Find a vector equation of the line \({{L}_{2}}\) which passes through \(O\) and \(P\).[3]
  2. Find an equation of the plane \(\pi \) containing both \({{L}_{1}}\) and \({{L}_{2}}\), in the scalar product form.[2]
  3. The points \(A\) and \(C\) are on different sides of \(\pi \) such that \(AC\) is perpendicular to \(\pi \). The distance of \(C\) from \(\pi \) is \(t\) times the distance of \(A\) from \(\pi \). Find, in terms of \(t\), the position vector of \(C\).[5]
  4. Find the value of \(t\) such that the line \(OC\) is parallel to the plane with equation \(\mathbf{r}\cdot \left( \begin{matrix} 2 \\ 0 \\ 1 \\ \end{matrix} \right)=2\).[2]

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Answer:(i) \({L_2 : \mathbf{r} = \mu \begin{pmatrix} 4 \\ 3 \\ 0 \end{pmatrix} ; \mu \in \mathbb{R}}\) (ii) \({\pi : \mathbf{r} \cdot \begin{pmatrix} -3 \\ 4 \\ 2 \end{pmatrix} = 0}\) (iii) \({\overrightarrow{OC} = \frac{1}{29} \begin{pmatrix} 60 - 27t \\ 7 + 36t \\ 76 + 18t \end{pmatrix}}\) (iv) \({t = \frac{49}{9}}\)

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