Section 34

Point Euclidean spaces

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Problem 34.1

Verify that the distance ρ(A,B)\rho (A, B) between points AA and BB in a point Euclidean space has the following properties:

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(1)

ρ(A,B)=ρ(B,A)\rho (A, B) = \rho (B, A) for any points AA and BB

(2)

ρ(A,B)⩽ρ(A,C)+ρ(B,C)\rho (A, B) \leqslant \rho (A, C) + \rho (B, C) for any points A,B,CA, B, C

(3)

for any point CC such that AC→=λAB→\overrightarrow {AC} = \lambda \overrightarrow {AB}, the equality ρ(A,C)=∣λ∣ρ(A,B)\rho (A, C) = \left|\lambda \right| \rho (A, B) holds.

Problem 34.2

Find the lengths of the sides and the interior angles of the triangle ABCABC given by the coordinates of its vertices:

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(1)

A(−1,0,−1,2),B(0,2,0,3),C(2,1,1,2)A(- 1, 0, - 1, 2), \quad B(0, 2, 0, 3), \quad C(2, 1, 1, 2)

(2)

A(1,2,2,−1),B(3,0,3,−1),C(2,1,1,0)A(1, 2, 2, - 1), B(3, 0, 3, - 1), \quad C(2, 1, 1, 0)

(3)

A(0,1,−1,2,−1),B(4,1,1,2,3),C(3,4,2,5,−1)A(0, 1, - 1, 2, - 1), \quad B(4, 1, 1, 2, 3), C(3, 4, 2, 5, - 1).

Problem 34.3

Prove that the set of points equidistant from two given distinct points AA and BB is the hyperplane passing through the midpoint of the segment ABAB perpendicular to this segment.

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Problem 34.4

Find the center and radius of the sphere circumscribed about the four-dimensional simplex given by the coordinates of its vertices:

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(1)

A0(4,−2,−1,−1),A1(1,1,2,2),A2(3,1,0,0)A_{0}(4, - 2, - 1, - 1), A_{1}(1, 1, 2, 2), A_{2}(3, 1, 0, 0), A3(0,2,3,−1),A4(1,−5,−4,2)A_{3}(0, 2, 3, - 1), \quad A_{4}(1, - 5, - 4, 2)

(2)

A0(3,3,1,−1),A1(1,3,3,1),A2(0,3,4,−1)A_{0}(3, 3, 1, - 1), A_{1}(1, 3, 3, 1), A_{2}(0, 3, 4, - 1), A3(2,1,2,3),A4(2,3,0,1)A_{3}(2, 1, 2, 3), \quad A_{4}(2, 3, 0, 1).

Problem 34.5

A hyperplane m\mathrm{m} in a four-dimensional point Euclidean space contains a tetrahedron given by the coordinates of its vertices: A1(4,4,−1,1),A2(−2,−8,−5,1)A_{1}(4, 4, - 1, 1), A_{2}(- 2, - 8, - 5, 1), A3(3,3,1,3),A4(1,−2,4,1)A_{3}(3, 3, 1, 3), A_{4}(1, - 2, 4, 1). The hyperplane m is regarded as a three-dimensional point Euclidean space. Find, in this space, the center and radius of the sphere circumscribed about the given tetrahedron.

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Problem 34.6

Prove that the distance from a point AA to a kk-dimensional plane m\mathrm{m} equals:

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(1)

the distance between the point AA and its orthogonal projection onto m\mathrm{m}

(2)

the length of the orthogonal component of the vector AB→(B\overrightarrow {AB}(B is an arbitrary point of m\mathrm{m}) with respect to the directing subspace of the plane m\mathrm{m}.

Problem 34.7

Let l\mathrm{l} and m\mathrm{m} be planes with directing subspaces L\mathcal{L} and M\mathcal{M} respectively, passing: l\mathrm{l} — through a point AA and m\mathrm{m} — through a point BB. Prove that the distance between the planes l\mathrm{l} and m\mathrm{m} equals the length of the orthogonal component of the vector AB→\overrightarrow {AB} with respect to the subspace L+M\mathcal{L} + \mathcal{M}.

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Problem 34.8

A hyperplane m\mathrm{m} is given by the equation a1x1+……+anxn+a0=0a_{1} x_{1} + \ldots \ldots + a_{n} x_{n} + a_{0} = 0. Prove that:

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(1)

the vector with coordinate column (a1,…,an)T\left(a_{1}, \ldots , a_{n}\right)^{T} is orthogonal to m

(2)

the distance from the point A(y1,…,yn)A\left(y_{1}, \ldots , y_{n}\right) to m equals

∣a1y1+…+anyn+a0∣/a12+…+an2. \left|a_{1} y_{1} + \ldots + a_{n} y_{n} + a_{0}\right| / \sqrt{a_{1}^{2} + \ldots + a_{n}^{2}}.
Problem 34.9

A point AA is given by coordinates, and a hyperplane m\mathrm{m} by an equation. Find the distance from AA to m\mathrm{m}, if:

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(1)

A(9,2,−3,1),m:3x1+x2−x3−5x4+3=0A(9, 2, - 3, 1), \quad \mathrm{m}: 3x_{1} + x_{2} - x_{3} - 5x_{4} + 3 = 0

(2)

A(1,−3,0,−2,4),m:2x1−5x2+x3+3x4+5x5−7=0A(1, - 3, 0, - 2, 4), \mathrm{m}: 2x_{1} - 5x_{2} + x_{3} + 3x_{4} + 5x_{5} - 7 = 0.

Problem 34.10

Write the equation of a hyperplane parallel to a hyperplane m\mathrm{m} and located at a given distance dd from m\mathrm{m}, if:

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(1)

m:5x1+2x2−4x3+2x4=3,d=2\mathrm{m}: 5x_{1} + 2x_{2} - 4x_{3} + 2x_{4} = 3, \quad d = 2

(2)

m:x1−4x2+2x3+2x4=4,d=5\mathrm{m}: x_{1} - 4x_{2} + 2x_{3} + 2x_{4} = 4, \quad d = 5

(3)

m:2x1−x2−x3+x4+3x5=−5,d=3\mathrm{m}: 2x_{1} - x_{2} - x_{3} + x_{4} + 3x_{5} = - 5, \quad d = 3.

Problem 34.11

Find the orthogonal projection of a point AA onto a hyperplane m\mathrm{m}:

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(1)

A(7,−1,6,1),m:3x1−x2+2x3+x4=5A(7, - 1, 6, 1), \quad \mathrm{m}: 3x_{1} - x_{2} + 2x_{3} + x_{4} = 5

(2)

A(1,2,8,−2)A(1, 2, 8, - 2), m: 2x1−2x3+x4=112x_{1} - 2x_{3} + x_{4} = 11

(3)

A(3,0,−1,2,6)A(3, 0, - 1, 2, 6), m: 5x1+3x2−2x3−x4+4x5=−165x_{1} + 3x_{2} - 2x_{3} - x_{4} + 4x_{5} = - 16.

Problem 34.12

Points AA and BB are given by their coordinates. Find the orthogonal projection of the vector AB‾\overline{AB} onto a hyperplane m\mathrm{m}, if:

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(1)

A(−3,0,1,3),B(5,2,2,3),m:2x1+x2−x4=3A(- 3, 0, 1, 3), \quad B(5, 2, 2, 3), \quad \mathrm{m}: 2x_{1} + x_{2} - x_{4} = 3

(2)

A(3,3,−8,−3,4),B(3,2,−1,−2,2),m:x1+x2−−2x3+x4+x5=5A(3, 3, - 8, - 3, 4), \quad B(3, 2, - 1, - 2, 2), \mathrm{m}: \quad x_{1} + x_{2} - - 2x_{3} + x_{4} + x_{5} = 5.

Problem 34.13

Find the ratio of the length of the orthogonal projection of an arbitrary edge of an nn-dimensional cube onto its diagonal to the length of the diagonal.

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Problem 34.14

Find the point orthogonally symmetric to a point AA with respect to a hyperplane m\mathrm{m}:

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(1)

A(5,5,3,3),m:2x1+3x2+x3+2x4+2=0A(5, 5, 3, 3), \quad \mathrm{m}: 2x_{1} + 3x_{2} + x_{3} + 2x_{4} + 2 = 0

(2)

A(3,5,−3,5),m:x1−3x2+4x3−5x4−2=0A(3, 5, - 3, 5), \mathrm{m}: x_{1} - 3x_{2} + 4x_{3} - 5x_{4} - 2 = 0

(3)

A(3,6,3,8,1),m:x1−x2−2x4+2x5−3=0A(3, 6, 3, 8, 1), \mathrm{m}: x_{1} - x_{2} - 2x_{4} + 2x_{5} - 3 = 0.

Problem 34.15

Find the orthogonal projection of a point AA onto a line:

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(1)

A(1,−5,2,0)A(1, - 5, 2, 0); l: x1=4+t,x2=3+2t,x3=−3−tx_{1} = 4 + t, \quad x_{2} = 3 + 2t, \quad x_{3} = - 3 - t, x4=7+3tx_{4} = 7 + 3t

(2)

A(−2,1,4,2)A(- 2, 1, 4, 2); l: x1=−3+2t,x2=3−t,x3=−1+tx_{1} = - 3 + 2t, \quad x_{2} = 3 - t, \quad x_{3} = - 1 + t, x4=−3+tx_{4} = - 3 + t

(3)

A(2,4,3,−1,1)A(2, 4, 3, - 1, 1); l: x1=2−2t,x2=−1+3t,x3=−1+2t,x4=2+t,x5=−tx_{1} = 2 - 2t, \quad x_{2} = - 1 + 3t, \quad x_{3} = - 1 + 2t, \quad x_{4} = 2 + t, \quad x_{5} = - t.

Problem 34.16

A point AA does not belong to a plane m\mathrm{m}. Prove that there exists a unique line passing through the point AA, intersecting m\mathrm{m} and perpendicular to m\mathrm{m}.

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Problem 34.17

Write the equations of the perpendicular dropped from a point AA onto a line l\mathrm{l}:

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(1)

A(1,−3,−2,4)A(1, - 3, - 2, 4); l: x1=4+3t,x2=2+t,x3=3+tx_{1} = 4 + 3t, \quad x_{2} = 2 + t, \quad x_{3} = 3 + t, x4=−1−tx_{4} = - 1 - t

(2)

A(1,−3,−1,3)A(1, - 3, - 1, 3); l: x1=2+t,x2=1−2t,x3=−1+2t,x4=tx_{1} = 2 + t, \quad x_{2} = 1 - 2t, \quad x_{3} = - 1 + 2t, \quad x_{4} = t

(3)

A(4,0,1,1,1)A(4, 0, 1, 1, 1); l: x1=t,x2=3−2t,x3=−2+tx_{1} = t, \quad x_{2} = 3 - 2t, \quad x_{3} = - 2 + t, x4=−3+2t,x5=tx_{4} = - 3 + 2t, \quad x_{5} = t.

Problem 34.18

Find the point orthogonally symmetric to a point AA with respect to a line l\mathrm{l}:

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(1)

A(4,1,−1,−1)A(4, 1, - 1, - 1), l\mathrm{l} is the line of problem 34.15,1)34. 15, 1)

(2)

A(2,5,−3,−2)A(2, 5, - 3, - 2), l\mathrm{l} is the line of problem 34.15,2)34. 15, 2).

Problem 34.19

Find the angle between a vector given by the coordinate column a, and a hyperplane m\mathrm{m}, if:

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(1)

a=[0101], m:3x1−x2+x3−5x4=2\mathbf{a} = \left[\begin{smallmatrix} 0\\ 1\\ 0\\ 1\end{smallmatrix}\right], \quad \mathrm{~ m}: 3x_{1} - x_{2} + x_{3} - 5x_{4} = 2

(2)

a=[1−111], m:3x1−x2+2x3+2x4=5\mathbf{a} = \left[\begin{smallmatrix} 1\\ - 1\\ 1\\ 1\end{smallmatrix}\right], \quad \mathrm{~ m}: 3x_{1} - x_{2} + 2x_{3} + 2x_{4} = 5

(3)

a=[1−32−1−1], m:x1+x2−2x3+3x4−x5=1\mathbf{a} = \left[\begin{smallmatrix} 1\\ - 3\\ 2\\ - 1\\ - 1\end{smallmatrix}\right], \quad \mathrm{~ m}: x_{1} + x_{2} - 2x_{3} + 3x_{4} - x_{5} = 1.

Problem 34.20

Find the angle between the lines l1l_{1} and l2l_{2}, if:

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(1)

l1:x1=4+t,x2=−2t,x3=1−t,x4=2;l2:x1=3l_{1}: x_{1} = 4 + t, x_{2} = - 2t, x_{3} = 1 - t, x_{4} = 2; l_{2}: x_{1} = 3, x2=t,x3=5+t,x4=−1x_{2} = t, \quad x_{3} = 5 + t, \quad x_{4} = - 1

(2)

l1:x1=1+t,x2=2+t,x3=3+t,x4=2t,x5=1−t;l2:x1=t,x2=5,x3=−1+t,x4=3−2t,x5=2t\mathrm{l}_{1}: x_{1} = 1 + t, \quad x_{2} = 2 + t, \quad x_{3} = 3 + t, \quad x_{4} = 2t, \quad x_{5} = 1 - t; \quad \mathrm{l}_{2}: x_{1} = t, \quad x_{2} = 5, \quad x_{3} = - 1 + t, \quad x_{4} = 3 - 2t, \quad x_{5} = 2t.

Problem 34.21

Find the distance from a point AA to a line l\mathrm{l}:

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(1)

A(0,3,2,−5)A(0, 3, 2, - 5); l: x1=1+t,x2=−t,x3=2+2tx_{1} = 1 + t, \quad x_{2} = - t, x_{3} = 2 + 2t, x4=−2+2tx_{4} = - 2 + 2t

(2)

A(2,−2,1,5);l:x1=3+t,x2=−1+t,x3=2+tA(2, - 2, 1, 5); \quad \mathrm{l}: x_{1} = 3 + t, \quad x_{2} = - 1 + t, \quad x_{3} = 2 + t, x4=−tx_{4} = - t

(3)

A(3,3,1,0,0);l:x1=2+3t,x2=1+2t,x3=−tA(3, 3, 1, 0, 0); \quad \mathrm{l}: \quad x_{1} = 2 + 3t, \quad x_{2} = 1 + 2t, \quad x_{3} = - t, x4=1+t,x5=−1−tx_{4} = 1 + t, \quad x_{5} = - 1 - t

(4)

A(1,−1,−1,1)A(1, - 1, - 1, 1); l: x1+x2+2x3+1=0,3x2+2x3−−x4−1=0,x1−x2+x3+x4+2=0x_{1} + x_{2} + 2x_{3} + 1 = 0, \quad 3x_{2} + 2x_{3} - - x_{4} - 1 = 0, x_{1} - x_{2} + x_{3} + x_{4} + 2 = 0.

Problem 34.22

A line l1l_{1} with directing vector a1a_{1} passes through a point A1A_{1}, and a line l2\mathrm{l}_{2} with directing vector a2a_{2} passes through a point A2A_{2}. Prove that:

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(1)

if a1a_{1} and a2a_{2} are not collinear, then the square of the distance between l1l_{1} and l2l_{2} equals det⁡Γ(A1A2→,a1,a2)/det⁡Γ(a1,a2)\operatorname {det} \Gamma \left(\overrightarrow {A_{1} A_{2}}, a_{1}, a_{2}\right) / \operatorname {det} \Gamma \left(a_{1}, a_{2}\right)

(2)

if a1a_{1} and a2a_{2} are collinear, then the square of the distance between l1l_{1} and l2l_{2} equals det⁡Γ(A1A2→,a1)/∣a1∣2\operatorname {det} \Gamma \left(\overrightarrow {A_{1} A_{2}}, a_{1}\right) / \left|a_{1}\right|^{2}.

Problem 34.23

Find the distance between the lines l1l_{1} and l2\mathrm{l}_{2}:

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(1)

l1:x1=1+t,x2=−1,x3=−t,x4=−2+t\mathrm{l}_{1}: \quad x_{1} = 1 + t, \quad x_{2} = - 1, \quad x_{3} = - t, \quad x_{4} = - 2 + t; l2:x1=4+t,x2=2t,x3=1+t,x4=t\mathrm{l}_{2}: x_{1} = 4 + t, \quad x_{2} = 2t, \quad x_{3} = 1 + t, \quad x_{4} = t

(2)

l1:x1=2+t,x2=−1−2t,x3=2+2t,x4=1−t\mathrm{l}_{1}: \quad x_{1} = 2 + t, \quad x_{2} = - 1 - 2t, \quad x_{3} = 2 + 2t, \quad x_{4} = 1 - t; l2:x1=3−t,x2=1+2t,x3=−1−2t,x4=2+tl_{2}: x_{1} = 3 - t, \quad x_{2} = 1 + 2t, \quad x_{3} = - 1 - 2t, \quad x_{4} = 2 + t

(3)

l1:x1=3+t,x2=2,x3=t,x4=3+t,x5=−t\mathrm{l}_{1}: \quad x_{1} = 3 + t, \quad x_{2} = 2, \quad x_{3} = t, \quad x_{4} = 3 + t, \quad x_{5} = - t; l2:x1=1+2t,x2=2t,x3=1−t,x4=t,x5=2l_{2}: x_{1} = 1 + 2t, \quad x_{2} = 2t, \quad x_{3} = 1 - t, \quad x_{4} = t, \quad x_{5} = 2

(4)

l1:x1=1+t,x2=2t,x3=1−t,x4=−1+t,x5=tl_{1}: x_{1} = 1 + t, \quad x_{2} = 2t, \quad x_{3} = 1 - t, \quad x_{4} = - 1 + t, \quad x_{5} = t; l2:x1=3+t,x2=−2t,x3=−1−t,x4=1+t,x5=2+tl_{2}: x_{1} = 3 + t, \quad x_{2} = - 2t, \quad x_{3} = - 1 - t, \quad x_{4} = 1 + t, \quad x_{5} = 2 + t

(5)

l1:x1=1−2t,x2=0,x3=t,x4=1+t,x5=2\mathrm{l}_{1}: \quad x_{1} = 1 - 2t, \quad x_{2} = 0, \quad x_{3} = t, \quad x_{4} = 1 + t, \quad x_{5} = 2; l2:x1=−1+t,x2=−1+t,x3=0,x4=1,x5=−2−tl_{2}: x_{1} = - 1 + t, \quad x_{2} = - 1 + t, \quad x_{3} = 0, \quad x_{4} = 1, \quad x_{5} = - 2 - t.

Problem 34.24

Write the equations of the perpendicular dropped from a point AA onto a plane m\mathrm{m}, if:

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(1)

A(3,7,−2,1);m:x1=2+t1,x2=2+t2,x3=t1+t2,x4=−t2A(3, 7, - 2, 1); \mathrm{m}: x_{1} = 2 + t_{1}, \quad x_{2} = 2 + t_{2}, \quad x_{3} = t_{1} + t_{2}, \quad x_{4} = - t_{2}

(2)

A(−3,−1,4,7,−3);m:x1=t1+t3,x2=2+t2+t3A(- 3, - 1, 4, 7, - 3); \mathrm{m}: x_{1} = t_{1} + t_{3}, \quad x_{2} = 2 + t_{2} + t_{3}, x3=2+t1,x4=1+t2+t3,x5=1+t2x_{3} = 2 + t_{1}, \quad x_{4} = 1 + t_{2} + t_{3}, \quad x_{5} = 1 + t_{2}.

Problem 34.25

Find the orthogonal projection of a point AA onto a plane m\mathrm{m}, if:

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(1)

A(−3,2,2,−2);m:x1=2+t1+t2,x2=4+2t1A(- 3, 2, 2, - 2); \mathrm{m}: x_{1} = 2 + t_{1} + t_{2}, \quad x_{2} = 4 + 2t_{1}, x3=t1,x4=−t2x_{3} = t_{1}, \quad x_{4} = - t_{2}

(2)

A(3,2,1,4,−1)A(3, 2, 1, 4, - 1); m:x1=1+t1,x2=−1+t2,x3=2+t1+t2,x4=−2−t1,x5=t2\mathrm{m}: x_{1} = 1 + t_{1}, \quad x_{2} = - 1 + t_{2}, \quad x_{3} = 2 + t_{1} + t_{2}, \quad x_{4} = - 2 - t_{1}, \quad x_{5} = t_{2}

(3)

A(0,−1,5,1,−2)A(0, - 1, 5, 1, - 2); m: x1=1+t1,x2=t3,x3=1+t1+t2,x4=−2+t3,x5=−1+t2x_{1} = 1 + t_{1}, \quad x_{2} = t_{3}, \quad x_{3} = 1 + t_{1} + t_{2}, \quad x_{4} = - 2 + t_{3}, \quad x_{5} = - 1 + t_{2}.

Problem 34.26

Find the point orthogonally symmetric to a point AA with respect to a plane m\mathrm{m}, if:

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(1)

A(5,3,−1,−1);m:x1=1+t1,x2=t2,x3=−2+t2,x4=−1+t1A(5, 3, - 1, - 1); \mathrm{m}: \quad x_{1} = 1 + t_{1}, \quad x_{2} = t_{2}, \quad x_{3} = - 2 + t_{2}, \quad x_{4} = - 1 + t_{1}

(2)

A(3,5,0,2,2);m:x1=t1,x2=2+t2,x3=−3+t1A(3, 5, 0, 2, 2); \mathrm{m}: x_{1} = t_{1}, \quad x_{2} = 2 + t_{2}, \quad x_{3} = - 3 + t_{1}, x4=3−t1−t2,x5=1x_{4} = 3 - t_{1} - t_{2}, \quad x_{5} = 1.

Problem 34.27

Let m\mathrm{m} be a plane with directing subspace M\mathcal{M}, passing through a point A0A_{0}, and let f1,…,fkf_{1}, \ldots , f_{k} be a basis in M\mathcal{M}. Prove that the square of the distance from a point A1A_{1} to the plane m\mathrm{m} equals

det⁡Γ(A0A1→,f1,…,fk)/det⁡Γ(f1,…,fk) \operatorname {det} \Gamma \left(\overrightarrow {A_{0} A_{1}}, f_{1}, \ldots , f_{k}\right) / \operatorname {det} \Gamma \left(f_{1}, \ldots , f_{k}\right)
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Problem 34.28

Find the distance from a point AA to a plane m:

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(1)

in problem 34.24,1)34. 24, 1)

(2)

in problem 34.24,2)34. 24, 2).

Problem 34.29

Find the distance from a point AA to a plane m\mathrm{m} given parametrically, if:

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(1)

A(1,2,1,1);m:x1=−2t1+4t2,x2=−1+t1−t2A(1, 2, 1, 1); \mathrm{m}: \quad x_{1} = - 2t_{1} + 4t_{2}, \quad x_{2} = - 1 + t_{1} - t_{2}, x3=−t3,x4=t1−t2x_{3} = - t_{3}, \quad x_{4} = t_{1} - t_{2}

(2)

A(3,1,1,0)A(3, 1, 1, 0); m:x1=−2+t1,x2=−t1+2t2,x3=t1−t2,x4=1−t1−t2\mathrm{m}: x_{1} = - 2 + t_{1}, \quad x_{2} = - t_{1} + 2t_{2}, \quad x_{3} = t_{1} - t_{2}, \quad x_{4} = 1 - t_{1} - t_{2}

(3)

A(1,2,1,3,0)A(1, 2, 1, 3, 0); m:x1=1+t1,x2=−t1+t2,x3=1+t2,x4=−1−t2,x5=t1\mathrm{m}: \quad x_{1} = 1 + t_{1}, \quad x_{2} = - t_{1} + t_{2}, \quad x_{3} = 1 + t_{2}, \quad x_{4} = - 1 - t_{2}, \quad x_{5} = t_{1}.

Problem 34.30

Find the distance from a point AA to a plane m\mathrm{m} given by a system of linear equations, if:

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(1)

A(1,0,0,1)A(1, 0, 0, 1); m: x1+2x2+2x3−3x4=7,x1−2x3+2x4=−6x_{1} + 2x_{2} + 2x_{3} - 3x_{4} = 7, \quad x_{1} - 2x_{3} + 2x_{4} = - 6

(2)

A(1,2,0,0)A(1, 2, 0, 0); m: x1+x2−x3−x4=1,2x2−3x3+x4=2,2x1+x3−3x4=0x_{1} + x_{2} - x_{3} - x_{4} = 1, \quad 2x_{2} - 3x_{3} + x_{4} = 2, \quad 2x_{1} + x_{3} - 3x_{4} = 0.

Problem 34.31

Points AA and BB are given by their coordinates. Find the angle between the vector AB‾\overline{AB} and a plane m\mathrm{m}, if:

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(1)

A(1,2,2,3),B(4,0,0,2);m:x1=1+t1,x2=2+t2,x3=−t1+t2,x4=3A(1, 2, 2, 3), \quad B(4, 0, 0, 2); \mathrm{m}: x_{1} = 1 + t_{1}, \quad x_{2} = 2 + t_{2}, \quad x_{3} = - t_{1} + t_{2}, \quad x_{4} = 3

(2)

A(0,1,−1,0,1),B(3,1,0,1,2);m:x1=t1+t2,x2=5A(0, 1, - 1, 0, 1), B(3, 1, 0, 1, 2); \mathrm{m}: x_{1} = t_{1} + t_{2}, x_{2} = 5, x3=−t2,x4=−t1+t2,x5=2+t1x_{3} = - t_{2}, \quad x_{4} = - t_{1} + t_{2}, \quad x_{5} = 2 + t_{1}

(3)

A(−1,−1,1,0,1),B(2,1,1,1,0)A(- 1, - 1, 1, 0, 1), \quad B(2, 1, 1, 1, 0); m: x1=t1+t3x_{1} = t_{1} + t_{3}, x2=2+t2,x3=1−t2,x4=−t1+t3,x5=−2t3x_{2} = 2 + t_{2}, \quad x_{3} = 1 - t_{2}, \quad x_{4} = - t_{1} + t_{3}, \quad x_{5} = - 2t_{3}.

Problem 34.32

Planes l\mathrm{l} and m\mathrm{m} of an nn-dimensional point Euclidean space, with directing subspaces L\mathcal{L} and M\mathcal{M} respectively, pass: l\mathrm{l} — through a point AA,  m\mathrm{~ m} — through a point BB. Let g1,…,gkg_{1}, \ldots , g_{k} be a basis in the subspace L+M\mathcal{L} + \mathcal{M}. Prove that the square of the distance between the planes l\mathrm{l} and m\mathrm{m} equals

det⁡Γ(AB→,g1,…,gk)/det⁡Γ(g1,…,gk).  \operatorname {det} \Gamma \left(\overrightarrow {AB}, g_{1}, \ldots , g_{k}\right) / \operatorname {det} \Gamma \left(g_{1}, \ldots , g_{k}\right) \text{. }
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Problem 34.33

Find the distance between the planes l\mathrm{l} and m\mathrm{m}:

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(1)

l: x1=2−2t,x2=4+t,x3=1+t,x4=0x_{1} = 2 - 2t, \quad x_{2} = 4 + t, \quad x_{3} = 1 + t, \quad x_{4} = 0; m:x1=1−2t1,x2=1+2t1+3t2,x3=1+t1,x4=1+2t1+2t2\mathrm{m}: x_{1} = 1 - 2t_{1}, \quad x_{2} = 1 + 2t_{1} + 3t_{2}, \quad x_{3} = 1 + t_{1}, \quad x_{4} = 1 + 2t_{1} + 2t_{2}

(2)

l: x1=3+t1+2t2,x2=−t1,x3=1+t1−t2x_{1} = 3 + t_{1} + 2t_{2}, \quad x_{2} = - t_{1}, \quad x_{3} = 1 + t_{1} - t_{2}, x4=−t1−t2;m:x1=2t1+t2,x2=1−3t1+t2x_{4} = - t_{1} - t_{2}; \quad \mathrm{m}: \quad x_{1} = 2t_{1} + t_{2}, \quad x_{2} = 1 - 3t_{1} + t_{2}, x3=−8−t2,x4=1+t1−t2x_{3} = - 8 - t_{2}, x_{4} = 1 + t_{1} - t_{2}

(3)

l: x1=2+t,x2=2t,x3=1,x4=t,x5=0x_{1} = 2 + t, \quad x_{2} = 2t, \quad x_{3} = 1, \quad x_{4} = t, \quad x_{5} = 0; m:x1=0,x2=1+t1+t2,x3=3+2t2,x4=2t1,x5=1+t1−t2\mathrm{m}: \quad x_{1} = 0, \quad x_{2} = 1 + t_{1} + t_{2}, \quad x_{3} = 3 + 2t_{2}, \quad x_{4} = 2t_{1}, \quad x_{5} = 1 + t_{1} - t_{2}

(4)

l: x1=1+t2,x2=t2,x3=t1,x4=t1,x5=2t1x_{1} = 1 + t_{2}, \quad x_{2} = t_{2}, \quad x_{3} = t_{1}, \quad x_{4} = t_{1}, \quad x_{5} = 2t_{1}; m:x1=t2+2t3,x2=2+t1+2t3,x3=x4=1+t1−t2+t3\mathrm{m}: x_{1} = t_{2} + 2t_{3}, \quad x_{2} = 2 + t_{1} + 2t_{3}, \quad x_{3} = x_{4} = 1 + t_{1} - t_{2} + t_{3}, x5=2+t1−t2+2t3x_{5} = 2 + t_{1} - t_{2} + 2t_{3}

(5)

l: 2x1−x3+3x4=0,2x1−2x2+3x3−3x4=82x_{1} - x_{3} + 3x_{4} = 0, \quad 2x_{1} - 2x_{2} + 3x_{3} - 3x_{4} = 8; m:x2=−3x3−2x4=2,x1−x3−x4=0\mathrm{m}: x_{2} = - 3x_{3} - 2x_{4} = 2, \quad x_{1} - x_{3} - x_{4} = 0

(6)

l: x1+x2−x3=1,2x1+x2−x4=4x_{1} + x_{2} - x_{3} = 1, \quad 2x_{1} + x_{2} - x_{4} = 4; m: x1+x2+x3=−1,x1+x3+x4=1,2x1−x2−x4=0x_{1} + x_{2} + x_{3} = - 1, \quad x_{1} + x_{3} + x_{4} = 1, \quad 2x_{1} - x_{2} - x_{4} = 0.

Problem 34.34

In an n-dimensional space, planes m1\mathrm{m}_{1} and m2\mathrm{m}_{2} of dimensions k1k_{1} and k2k_{2} respectively are absolutely skew. Prove that:

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(1)

there exists a unique plane of dimension n−−k1−k2n - - k_{1} - k_{2}, orthogonal to m1\mathrm{m}_{1} and to m2\mathrm{m}_{2} and intersecting each of these planes

(2)

there exists a unique line, orthogonal to m1\mathrm{m}_{1} and to m2\mathrm{m}_{2} and intersecting each of these planes.

Problem 34.35

Find the equations of the plane of maximal dimension orthogonal to given planes m1\mathrm{m}_{1} and m2\mathrm{m}_{2} and intersecting each of these planes, as well as the equations of the common perpendicular to m1\mathrm{m}_{1} and m2\mathrm{m}_{2}, if:

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(1)

m1\mathrm{m}_{1} and m2\mathrm{m}_{2} are the lines of problem 34.23,134. 23, 1)

(2)

m1\mathrm{m}_{1} and m2\mathrm{m}_{2} are the lines of problem 34.23,334. 23, 3)

(3)

m1\mathrm{m}_{1} and m2\mathrm{m}_{2} are the planes of problem 34.33,334. 33, 3).

Problem 34.36

Find the angle between the planes m1:x1=2+t1+t2,x2=x3=t1,x4=−1+t1−t2\mathrm{m}_{1}: x_{1} = 2 + t_{1} + t_{2}, x_{2} = x_{3} = t_{1}, x_{4} = - 1 + t_{1} - t_{2} and m2:x1=t1+2t2,x2=3+t2,x3=2−t1−2t2,x4=−t2\mathrm{m}_{2}: x_{1} = t_{1} + 2t_{2}, x_{2} = 3 + t_{2}, x_{3} = 2 - t_{1} - 2t_{2}, x_{4} = - t_{2}.

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Problem 34.37

In a regular five-dimensional simplex A0A1A2A3A4A5A_{0} A_{1} A_{2} A_{3} A_{4} A_{5}, find the angle:

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(1)

between the faces A0A1A2A_{0} A_{1} A_{2} and A0A3A4A_{0} A_{3} A_{4}

(2)

between the faces A0A1A2A_{0} A_{1} A_{2} and A0A3A4A5A_{0} A_{3} A_{4} A_{5}

(3)

between the faces A0A1A2A_{0} A_{1} A_{2} and A1A2A3A4A5A_{1} A_{2} A_{3} A_{4} A_{5}.