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Vectors: planes, normals and distances

Practice section 2 of 7

Questions 7–12 in this collection

Practice questions

Worked example · 1 of 6

Find the acute angle between a line and a plane

Find the acute angle between

r=(1+λ)i+(2−λ)j+(λ−1)k,λ∈R,\mathbf r=(1+\lambda)\mathbf i+(2-\lambda)\mathbf j+(\lambda-1)\mathbf k,\quad\lambda\in\mathbb R,

and the plane r⋅(2i−j+k)=4\mathbf r\cdot(2\mathbf i-\mathbf j+\mathbf k)=4, to the nearest 0.1∘0.1^\circ.

CJC · Lecture · Example 34

Solution

Worked example · 4 of 6

Separate a line–plane distance from a point–plane distance

Find a vector equation of the line through A(3,1,2)A(3,1,2) perpendicular to the plane r⋅(2i−j+k)=4\mathbf r\cdot(2\mathbf i-\mathbf j+\mathbf k)=4.

(i) Find the intersection of the line and plane.

(ii) State the shortest distance from the line to the plane.

(iii) Find the shortest distance from A to the plane.

CJC · Lecture · Example 37

Solution

Worked example · 5 of 6

Explain parallel planes and project their separation

Two planes have equations

p1:r⋅(2,1,−2)=3,p2:r⋅(4,2,−4)=−9.\begin{aligned}p_1:\quad\mathbf r\cdot(2,1,-2)&=3,\\p_2:\quad\mathbf r\cdot(4,2,-4)&=-9.\end{aligned}

Explain why they are parallel and find the distance between them.

CJC · Lecture · Example 38

Solution

Worked example · 6 of 6

Read a common line from simultaneous plane equations

Find the equation of the line of intersection of r⋅(i+j−3k)=6\mathbf r\cdot(\mathbf i+\mathbf j-3\mathbf k)=6 and r⋅(2i−j+k)=4\mathbf r\cdot(2\mathbf i-\mathbf j+\mathbf k)=4.

CJC · Lecture · Example 39

Solution

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