Subsection 6.1

Vector equations of lines and planes (6.1-6.12)

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Problem 6.1

Write the equation of:

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(1)

the plane r=r0+au+bv\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} u + \mathbf{b} v in the form (r,n)=D(a∦b)(\mathbf{r}, \mathbf{n}) = D(\mathbf{a} \nparallel \mathbf{b})

(2)

the line r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t in the form [r,a]=b\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b} (a≠0)(\mathbf{a} \neq 0)

(3)

the line [r,a]=b\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b} in the form r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0)

(4)

the line (r,ni)=Di,i=1,2\left(\mathbf{r}, \mathbf{n}_{i}\right) = D_{i}, i = 1, 2, in the form [r,a]=b(n1∦n2)\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b}\left(\mathbf{n}_{1} \nparallel \mathbf{n}_{2}\right)

(5)

the line (r,ni)=Di,i=1,2\left(\mathbf{r}, \mathbf{n}_{i}\right) = D_{i}, i = 1, 2, in the form r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0).

Problem 6.2

Find the necessary and sufficient condition under which the planes (r,n1)=D1\left(\mathbf{r}, \mathbf{n}_{1}\right) = D_{1} and (r,n2)=D2(ni≠0,i=1,2)\left(\mathbf{r}, \mathbf{n}_{2}\right) = D_{2} \quad \left(\mathbf{n}_{i} \neq 0, i = 1, 2\right):

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(1)

intersect along a line

(2)

are parallel but do not coincide

(3)

coincide.

Problem 6.3

Find the necessary and sufficient condition under which the lines r=r1+a1t\mathbf{r} = \mathbf{r}_{1} + \mathbf{a}_{1} t and r=r2+a2t(ai≠0,i=1,2)\mathbf{r} = \mathbf{r}_{2} + \mathbf{a}_{2} t\left(\mathbf{a}_{i} \neq 0, i = 1, 2\right):

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(1)

intersect (i.e. have a unique common point)

(2)

are skew

(3)

are parallel but do not coincide

(4)

coincide.

Problem 6.4

Given a line r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0) and a plane (r,n)=D(n≠0)(\mathbf{r}, \mathbf{n}) = D (\mathbf{n} \neq 0). Under what necessary and sufficient condition:

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(1)

do they intersect (have a unique common point)

(2)

are they parallel (have no common points)

(3)

does the line lie in the plane?

Problem 6.5

Find the position vector of the point of intersection of:

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(1)

the line r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t with the plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D (if (a,n)≠0(\mathbf{a}, \mathbf{n}) \neq 0)

(2)

the line [r,a]=b\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b} with the plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D (if (a,n)≠0)(\mathbf{a}, \mathbf{n}) \neq 0)).

Problem 6.6

Point M0M_{0} is determined by the position vector r0\mathbf{r}_{0}. Find the equations of:

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(1)

the line passing through the point M0M_{0} perpendicular to the plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D

(2)

the plane passing through the point M0M_{0} perpendicular to the line r=r1+at\mathbf{r} = \mathbf{r}_{1} + \mathbf{at}.

Problem 6.7

Find the vector equation of the plane passing through the line r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0) and the point M1(r1)M_{1}\left(\mathbf{r}_{1}\right), not lying on this line.

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Problem 6.8

Given a point M0(r0)M_{0}\left(\mathbf{r}_{0}\right) and a plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D (n≠0)(\mathbf{n} \neq 0). Find the position vector of:

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(1)

the projection of point M0M_{0} onto the plane

(2)

the point M1M_{1} symmetric to M0M_{0} with respect to the plane.

Problem 6.9

Given a point M0(r0)M_{0}\left(\mathbf{r}_{0}\right) and a line r=r1+at\mathbf{r} = \mathbf{r}_{1} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0). Find the position vector of:

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(1)

the projection of point M0M_{0} onto the line

(2)

the point M1M_{1} symmetric to M0M_{0} with respect to the line.

Problem 6.10

Find the equations of:

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(1)

the projection onto the plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D (n≠0)(\mathbf{n} \neq 0) of the line r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0), not perpendicular to this plane

(2)

the line meeting the line r=r1+at\mathbf{r} = \mathbf{r}_{1} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0) at a right angle and passing through the point M0(r0)M_{0}\left(\mathbf{r}_{0}\right), not lying on the given line (the perpendicular dropped from the point M0(r0)M_{0}\left(\mathbf{r}_{0}\right) onto the line r=r1+at\mathbf{r} = \mathbf{r}_{1} + \mathbf{a} t)

(3)

the line meeting the two skew lines r=r1+a1t\mathbf{r} = \mathbf{r}_{1} + \mathbf{a}_{1} t and r=r2+a2t\mathbf{r} = \mathbf{r}_{2} + \mathbf{a}_{2} t (a≠0)(\mathbf{a} \neq 0) and passing through the point M0(r0)M_{0}\left(\mathbf{r}_{0}\right), not lying on either of these lines

(4)

the line meeting the two skew lines r=r1+a1t\mathbf{r} = \mathbf{r}_{1} + \mathbf{a}_{1} t and r=r2+a2t\mathbf{r} = \mathbf{r}_{2} + \mathbf{a}_{2} t (a≠0)(\mathbf{a} \neq 0) at right angles (the common perpendicular to these lines).

Problem 6.11

Find the distance:

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(1)

from the point M0(r0)M_{0}\left(\mathbf{r}_{0}\right) to the plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D (n≠0)(\mathbf{n} \neq 0)

(2)

between the two parallel planes r=r1+au+bv\mathbf{r} = \mathbf{r}_{1} + \mathbf{a} u + \mathbf{b} v and r=r2+au+bv\mathbf{r} = \mathbf{r}_{2} + \mathbf{a} u + \mathbf{b} v (a≠0)(\mathbf{a} \neq 0)

(3)

between the two parallel planes (r,n)=D1(\mathbf{r}, \mathbf{n}) = D_{1} and (r,n)=D2(\mathbf{r}, \mathbf{n}) = D_{2} (n≠0)(\mathbf{n} \neq 0)

(4)

from the point M0(r0)M_{0}\left(\mathbf{r}_{0}\right) to the line r=r1+at\mathbf{r} = \mathbf{r}_{1} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0)

(5)

from the point M0(r0)M_{0}\left(\mathbf{r}_{0}\right) to the line [r,a]=b\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b} (a≠0)(\mathbf{a} \neq 0)

(6)

between the two parallel lines r=r1+at\mathbf{r} = \mathbf{r}_{1} + \mathbf{a} t and r=r2+at\mathbf{r} = \mathbf{r}_{2} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0)

(7)

between the two parallel lines [r,a]=b1\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b}_{1} and [r,a]=b2\left[\mathbf{r}, \mathbf{a}\right] = \mathbf{b}_{2} (a≠0)(\mathbf{a} \neq 0)

(8)

between the two skew lines r=r1+a1t\mathbf{r} = \mathbf{r}_{1} + \mathbf{a}_{1} t and r=r2+a2t\mathbf{r} = \mathbf{r}_{2} + \mathbf{a}_{2} t (a≠0)(\mathbf{a} \neq 0)

(9)

between the two skew lines [r,a1]=b1\left[\mathbf{r}, \mathbf{a}_{1}\right] = \mathbf{b}_{1} and [r,a2]=b2\left[\mathbf{r}, \mathbf{a}_{2}\right] = \mathbf{b}_{2} (a≠0)(\mathbf{a} \neq 0).

Problem 6.12

Given a line r=r0+at\mathbf{r} = \mathbf{r}_{0} + \mathbf{a} t (a≠0)(\mathbf{a} \neq 0) and a plane (r,n)=D(\mathbf{r}, \mathbf{n}) = D (n≠0)(\mathbf{n} \neq 0), not parallel to each other. Point MM lies on the line and is at distance ρ\rho from the plane. Find the position vector of point MM.

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