2023 MI PRU1 P1 Q7

2023 MI PRU1 P1 Q7

11 marks
Promo

Relative to the origin \(O\), the point \(A\) has position vector \(3\mathbf{i}+7\mathbf{j}+\mathbf{k}\). The plane \(\pi \) contains \(A\) and is parallel to the vector \(-2\mathbf{i}+2\mathbf{j}+\mathbf{k}\) and the line \(\mathbf{r}=\alpha \left( -\mathbf{i}+2\mathbf{j}+3\mathbf{k} \right)\), where \(\alpha \in \mathbb{R}\).

  1. Show that the cartesian equation of plane \(\pi \) can be expressed as \(4x+5y-2z=45\).[3]

The point \(B\) has coordinates \(\left( 2,\ 0,\ 4 \right)\).

  1. Find the position vector of the point \(F\), the foot of the perpendicular from \(B\) to the plane \(\pi \).[3]
  2. Hence find the position vector of the point \({B}'\), the reflection of \(B\) in the plane \(\pi \).[2]
  3. Find angle \(BA{B}'\).[3]

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Answer:(ii) \(\overrightarrow{OF}=\left( \begin{matrix} \begin{matrix} 6 \\ 5 \\ 2 \\ \end{matrix} \\ \end{matrix} \right)\) (iii) \(\overrightarrow{OB'}=\left( \begin{matrix} \begin{matrix} 10 \\ 10 \\ 0 \\ \end{matrix} \\ \end{matrix} \right)\) (iv) \({{121.7}^{\circ }}\) (\(1\) d.p.)

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