Perpendicular distance point to line

10 With respect to the origin \(O\), the points \(A , B , C , D\) have position vectors given by $$\overrightarrow { O A } = 4 \mathbf { i } + \mathbf { k } , \quad \overrightarrow { O B } = 5 \mathbf { i } - 2 \mathbf { j } - 2 \mathbf { k } , \quad \overrightarrow { O C } = \mathbf { i } + \mathbf { j } , \quad \overrightarrow { O D } = - \mathbf { i } - 4 \mathbf { k }$$

1. Calculate the acute angle between the lines \(A B\) and \(C D\).
2. Prove that the lines \(A B\) and \(C D\) intersect.
3. The point \(P\) has position vector \(\mathbf { i } + 5 \mathbf { j } + 6 \mathbf { k }\). Show that the perpendicular distance from \(P\) to the line \(A B\) is equal to \(\sqrt { } 3\).

10 With respect to the origin \(O\), the points \(A , B\) and \(C\) have position vectors given by $$\overrightarrow { O A } = \left( \begin{array} { r } 3 \\ - 2 \\ 4 \end{array} \right) , \quad \overrightarrow { O B } = \left( \begin{array} { r } 2 \\ - 1 \\ 7 \end{array} \right) \quad \text { and } \quad \overrightarrow { O C } = \left( \begin{array} { r } 1 \\ - 5 \\ - 3 \end{array} \right) .$$ The plane \(m\) is parallel to \(\overrightarrow { O C }\) and contains \(A\) and \(B\).

1. Find the equation of \(m\), giving your answer in the form \(a x + b y + c z = d\).
2. Find the length of the perpendicular from \(C\) to the line through \(A\) and \(B\).

10 With respect to the origin \(O\), the points \(A , B\) and \(C\) have position vectors given by $$\overrightarrow { O A } = \left( \begin{array} { r } 3 \\ - 2 \\ 4 \end{array} \right) , \quad \overrightarrow { O B } = \left( \begin{array} { r } 2 \\ - 1 \\ 7 \end{array} \right) \quad \text { and } \quad \overrightarrow { O C } = \left( \begin{array} { r } 1 \\ - 5 \\ - 3 \end{array} \right)$$ The plane \(m\) is parallel to \(\overrightarrow { O C }\) and contains \(A\) and \(B\).

1. Find the equation of \(m\), giving your answer in the form \(a x + b y + c z = d\).
2. Find the length of the perpendicular from \(C\) to the line through \(A\) and \(B\).

9 With respect to the origin \(O\), the vertices of a triangle \(A B C\) have position vectors $$\overrightarrow { O A } = 2 \mathbf { i } + 5 \mathbf { k } , \quad \overrightarrow { O B } = 3 \mathbf { i } + 2 \mathbf { j } + 3 \mathbf { k } \quad \text { and } \quad \overrightarrow { O C } = \mathbf { i } + \mathbf { j } + \mathbf { k }$$

1. Using a scalar product, show that angle \(A B C\) is a right angle.
2. Show that triangle \(A B C\) is isosceles.
3. Find the exact length of the perpendicular from \(O\) to the line through \(B\) and \(C\).

9
\includegraphics[max width=\textwidth, alt={}, center]{c1fbc9ef-2dc6-43c3-bc58-179f683c9acf-16_696_1104_264_518} In the diagram, \(O A B C D E F G\) is a cuboid in which \(O A = 2\) units, \(O C = 4\) units and \(O G = 2\) units. Unit vectors \(\mathbf { i } , \mathbf { j }\) and \(\mathbf { k }\) are parallel to \(O A , O C\) and \(O G\) respectively. The point \(M\) is the midpoint of \(D F\). The point \(N\) on \(A B\) is such that \(A N = 3 N B\).

1. Express the vectors \(\overrightarrow { O M }\) and \(\overrightarrow { M N }\) in terms of \(\mathbf { i } , \mathbf { j }\) and \(\mathbf { k }\).
2. Find a vector equation for the line through \(M\) and \(N\).
3. Show that the length of the perpendicular from \(O\) to the line through \(M\) and \(N\) is \(\sqrt { \frac { 53 } { 6 } }\).

9 With respect to the origin \(O\), the point \(A\) has position vector given by \(\overrightarrow { O A } = \mathbf { i } + 5 \mathbf { j } + 6 \mathbf { k }\). The line \(l\) has vector equation \(\mathbf { r } = 4 \mathbf { i } + \mathbf { k } + \lambda ( - \mathbf { i } + 2 \mathbf { j } + 3 \mathbf { k } )\).

1. Find in degrees the acute angle between the directions of \(O A\) and \(l\).
2. Find the position vector of the foot of the perpendicular from \(A\) to \(l\).
3. Hence find the position vector of the reflection of \(A\) in \(l\).

8
\includegraphics[max width=\textwidth, alt={}, center]{8f81a526-783c-4321-b540-c9deccfee17b-12_639_713_262_715} In the diagram, \(O A B C D E F G\) is a cuboid in which \(O A = 2\) units, \(O C = 3\) units and \(O D = 2\) units. Unit vectors \(\mathbf { i } , \mathbf { j }\) and \(\mathbf { k }\) are parallel to \(O A , O C\) and \(O D\) respectively. The point \(M\) on \(A B\) is such that \(M B = 2 A M\). The midpoint of \(F G\) is \(N\).

1. Express the vectors \(\overrightarrow { O M }\) and \(\overrightarrow { M N }\) in terms of \(\mathbf { i } , \mathbf { j }\) and \(\mathbf { k }\).
2. Find a vector equation for the line through \(M\) and \(N\).
3. Find the position vector of \(P\), the foot of the perpendicular from \(D\) to the line through \(M\) and \(N\). [4]

8
\includegraphics[max width=\textwidth, alt={}, center]{bbe57fc0-a8a5-4fe5-a637-4f9db00bdc13-10_588_789_260_678} In the diagram, \(O A B C D\) is a pyramid with vertex \(D\). The horizontal base \(O A B C\) is a square of side 4 units. The edge \(O D\) is vertical and \(O D = 4\) units. The unit vectors \(\mathbf { i } , \mathbf { j }\) and \(\mathbf { k }\) are parallel to \(O A , O C\) and \(O D\) respectively. The midpoint of \(A B\) is \(M\) and the point \(N\) on \(C D\) is such that \(D N = 3 N C\).

1. Find a vector equation for the line through \(M\) and \(N\).
2. Show that the length of the perpendicular from \(O\) to \(M N\) is \(\frac { 1 } { 3 } \sqrt { 82 }\).
   \(9 \quad\) Let \(\mathrm { f } ( x ) = \frac { 1 } { ( 9 - x ) \sqrt { x } }\).

10 The equations of the lines \(l\) and \(m\) are given by $$l : \mathbf { r } = \left( \begin{array} { r } 3 \\ - 2 \\ 1 \end{array} \right) + \lambda \left( \begin{array} { l } 1 \\ 1 \\ 2 \end{array} \right) \quad \text { and } \quad m : \mathbf { r } = \left( \begin{array} { r } 6 \\ - 3 \\ 6 \end{array} \right) + \mu \left( \begin{array} { r } - 2 \\ 4 \\ c \end{array} \right)$$ where \(c\) is a positive constant. It is given that the angle between \(l\) and \(m\) is \(60 ^ { \circ }\).

1. Find the value of \(c\).
2. Show that the length of the perpendicular from \(( 6 , - 3,6 )\) to \(l\) is \(\sqrt { 11 }\).

1. With respect to a fixed origin \(O\), the lines \(l _ { 1 }\) and \(l _ { 2 }\) are given by the equations

$$l _ { 1 } : \mathbf { r } = \left( \begin{array} { r } 12 \\ - 4 \\ 5 \end{array} \right) + \lambda \left( \begin{array} { r } 5 \\ - 4 \\ 2 \end{array} \right) , \quad l _ { 2 } : \mathbf { r } = \left( \begin{array} { l } 2 \\ 2 \\ 0 \end{array} \right) + \mu \left( \begin{array} { l } 0 \\ 6 \\ 3 \end{array} \right)$$ where \(\lambda\) and \(\mu\) are scalar parameters.

1. Show that \(l _ { 1 }\) and \(l _ { 2 }\) meet, and find the position vector of their point of intersection \(A\).
2. Find, to the nearest \(0.1 ^ { \circ }\), the acute angle between \(l _ { 1 }\) and \(l _ { 2 }\) The point \(B\) has position vector \(\left( \begin{array} { l } 7 \\ 0 \\ 3 \end{array} \right)\).
3. Show that \(B\) lies on \(l _ { 1 }\)
4. Find the shortest distance from \(B\) to the line \(l _ { 2 }\), giving your answer to 3 significant figures.

7. The plane \(\Pi\) has vector equation $$\mathbf { r } = 3 \mathbf { i } + \mathbf { k } + \lambda ( - 4 \mathbf { i } + \mathbf { j } ) + \mu ( 6 \mathbf { i } - 2 \mathbf { j } + \mathbf { k } )$$

1. Find an equation of \(\Pi\) in the form \(\mathbf { r } \cdot \mathbf { n } = p\), where \(\mathbf { n }\) is a vector perpendicular to \(\Pi\) and \(p\) is a constant. The point \(P\) has coordinates \(( 6,13,5 )\). The line \(l\) passes through \(P\) and is perpendicular to \(\Pi\). The line \(l\) intersects \(\Pi\) at the point \(N\).
2. Show that the coordinates of \(N\) are \(( 3,1 , - 1 )\). The point \(R\) lies on \(\Pi\) and has coordinates \(( 1,0,2 )\).
3. Find the perpendicular distance from \(N\) to the line \(P R\). Give your answer to 3 significant figures.

6．The lines \(L _ { 1 }\) and \(L _ { 2 }\) have vector equations $$\begin{aligned} & L _ { 1 } : \mathbf { r } = \left( \begin{array} { r } 1 \\ 10 \\ - 3 \end{array} \right) + \lambda \left( \begin{array} { r } 2 \\ - 5 \\ 4 \end{array} \right) \\ & L _ { 2 } : \mathbf { r } = \left( \begin{array} { r } - 1 \\ 2 \\ 3 \end{array} \right) + \mu \left( \begin{array} { l } 1 \\ 2 \\ 2 \end{array} \right) \end{aligned}$$ （a）Show that \(L _ { 1 }\) and \(L _ { 2 }\) are perpendicular．
（b）Show that \(L _ { 1 }\) and \(L _ { 2 }\) are skew lines． The point \(A\) with position vector \(- \mathbf { i } + 2 \mathbf { j } + 3 \mathbf { k }\) lies on \(L _ { 2 }\) and the point \(X\) lies on \(L _ { 1 }\) such that \(\overrightarrow { A X }\) is perpendicular to \(L _ { 1 }\)
（c）Find the position vector of \(X\) ．
（d）Find \(| \overrightarrow { A X } |\) The point \(B\)（distinct from \(A\) ）also lies on \(L _ { 2 }\) and \(| \overrightarrow { B X } | = | \overrightarrow { A X } |\)
（e）Find the position vector of \(B\) ．
（f）Find the cosine of angle \(A X B\) ．

8
\includegraphics[max width=\textwidth, alt={}, center]{258f9a6f-9339-49c3-8118-6ae9e934f1bb-14_503_727_251_669} In th id ag am, \(O A B C\) is a ply amid in wh ch \(O A = 2\) in ts, \(O B = 4\) in ts ad \(O C = 2\) in ts. Th ed \(O C\) is rtical, th \(\mathbf { b }\) se \(O A B\) is \(\mathbf { b }\) izd al ad ag e \(A O B = \theta ^ { \circ }\). Un t cto s \(\mathbf { i } , \mathbf { j }\) ad \(\mathbf { k }\) are \(\mathbf { p }\) rallel to \(O A\), \(O B\) ad \(O C\) resp ctie ly. Th mij nsg \(A B\) ad \(B C\) are \(M\) ad \(N\) resp ctie ly.

1. Eq ess th cto s \(\overrightarrow { \mathrm { ON } }\) ad \(\overrightarrow { \mathrm { CM } }\) irt erms \(\boldsymbol { 6 } \mathbf { i } , \mathbf { j }\) ad \(\mathbf { k }\).
2. Calch ate th ab eb tweert b di rectis \(6 \overrightarrow { \mathrm { ON } }\) ad \(\overrightarrow { \mathrm { CM } }\).
3. Sth the leg lo th p rp d ich ar from \(M\) to \(O N\) is \(\frac { 3 } { 5 } \sqrt { 5 }\).

15

1. Show that the three planes with equations $$\begin{aligned} x + \lambda y + 3 z & = - 12 \\ 2 x + y + 5 z & = - 11 \\ x - 2 y + 2 z & = - 9 \end{aligned}$$ where \(\lambda\) is a constant, meet at a unique point except for one value of \(\lambda\) which is to be determined.
2. In the case \(\lambda = - 2\), use matrices to find the point of intersection P of the planes, showing your method clearly. The line \(l\) has equation \(\frac { x - 1 } { 2 } = \frac { y - 1 } { - 1 } = \frac { z + 2 } { - 2 }\).
3. Find a vector equation of \(l\).
4. Find the shortest distance between the point P and \(l\).
5. 1. Show that \(l\) is parallel to the plane \(x - 2 y + 2 z = - 9\).
   2. Find the distance between \(l\) and the plane \(x - 2 y + 2 z = - 9\).

1. The plane \(\Pi\) has vector equation

$$\mathbf { r } = 3 \mathbf { i } + \mathbf { k } + \lambda ( - 4 \mathbf { i } + \mathbf { j } ) + \mu ( 6 \mathbf { i } - 2 \mathbf { j } + \mathbf { k } )$$

1. Find an equation of \(\Pi\) in the form \(\mathbf { r } . \mathbf { n } = p\), where \(\mathbf { n }\) is a vector perpendicular to \(\Pi\) and \(p\) is a constant. The point \(P\) has coordinates \(( 6,13,5 )\). The line \(l\) passes through \(P\) and is perpendicular to \(\Pi\). The line \(l\) intersects \(\Pi\) at the point \(N\).
2. Show that the coordinates of \(N\) are \(( 3,1 , - 1 )\). The point \(R\) lies on \(\Pi\) and has coordinates \(( 1,0,2 )\).
3. Find the perpendicular distance from \(N\) to the line \(P R\). Give your answer to 3 significant figures.