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Three Dimensional Geometry

Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.

Direction cosines and direction ratios of a line

Subtopic

Direction cosines and direction ratios of a line under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    The direction ratios of two lines are (2,3,6)(2, 3, 6) and (1,2,2)(1, 2, 2). Find the sum of the products of their corresponding direction ratios.

    A.

    2020

    B.

    1010

    C.

    00

    D.

    1515

  2. 2.

    Find the direction cosines of a line joining the origin to the point (1,2,3)(1, 2, 3).

    A.

    (114,214,314)(\frac{1}{14}, \frac{2}{14}, \frac{3}{14})

    B.

    (114,214,314)(\frac{1}{\sqrt{14}}, \frac{2}{\sqrt{14}}, \frac{3}{\sqrt{14}})

    C.

    (1,2,3)(1, 2, 3)

    D.

    (16,26,36)(\frac{1}{6}, \frac{2}{6}, \frac{3}{6})

  3. 3.

    The coordinates of a point PP are (x,y,z)(x, y, z) and the direction cosines of the line OPOP are l,m,nl, m, n. If OP=rOP = r, then xx is equal to:

    A.

    lrlr

    B.

    mrmr

    C.

    nrnr

    D.

    lr\frac{l}{r}

Download the worksheet for Three Dimensional Geometry - Direction cosines and direction ratios of a line to practice offline. It includes additional chapter-level practice questions.

Cartesian equation and vector equation of a line

Subtopic

Cartesian equation and vector equation of a line under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    The direction cosines l,m,nl, m, n of a line satisfy l2+m2+n2=1l^2 + m^2 + n^2 = 1. If l=m=nl=m=n, find the value of ll.

    A.

    ±13\pm \frac{1}{\sqrt{3}}

    B.

    13\frac{1}{3}

    C.

    11

    D.

    ±13\pm \frac{1}{3}

  2. 2.

    What is the distance of the point (2,3,4)(2, 3, 4) from the xx-axis?

    A.

    55

    B.

    13\sqrt{13}

    C.

    20\sqrt{20}

    D.

    22

  3. 3.

    Are the lines x−57=y+2−5=z1\frac{x-5}{7} = \frac{y+2}{-5} = \frac{z}{1} and x1=y2=z3\frac{x}{1} = \frac{y}{2} = \frac{z}{3} perpendicular?

    A.

    Yes, because a1a2+b1b2+c1c2=0a_1 a_2 + b_1 b_2 + c_1 c_2 = 0

    B.

    No, because the dot product of direction vectors is not zero

    C.

    Yes, because they intersect at the origin

    D.

    No, because they are parallel

Download the worksheet for Three Dimensional Geometry - Cartesian equation and vector equation of a line to practice offline. It includes additional chapter-level practice questions.

Coplanar and skew lines, shortest distance between two lines

Subtopic

Coplanar and skew lines, shortest distance between two lines under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    Which of the following is true for two skew lines?

    A.

    They are always parallel

    B.

    They never intersect and are not parallel

    C.

    They must lie in the same plane

    D.

    They always intersect at a right angle

  2. 2.

    The lines x−x1a1=y−y1b1=z−z1c1\frac{x-x_1}{a_1} = \frac{y-y_1}{b_1} = \frac{z-z_1}{c_1} and x−x2a2=y−y2b2=z−z2c2\frac{x-x_2}{a_2} = \frac{y-y_2}{b_2} = \frac{z-z_2}{c_2} are parallel if:

    A.

    a1a2+b1b2+c1c2=0a_1a_2 + b_1b_2 + c_1c_2 = 0

    B.

    a1a2=b1b2=c1c2\frac{a_1}{a_2} = \frac{b_1}{b_2} = \frac{c_1}{c_2}

    C.

    a1=a2,b1=b2,c1=c2a_1=a_2, b_1=b_2, c_1=c_2 only

    D.

    a1/x1=a2/x2a_1/x_1 = a_2/x_2

  3. 3.

    What is the relation between the shortest distance dd and the coplanarity of two lines?

    A.

    d>0d > 0 for coplanar lines

    B.

    d=0d = 0 for coplanar lines

    C.

    d=1d = 1 for coplanar lines

    D.

    dd is undefined for coplanar lines

Download the worksheet for Three Dimensional Geometry - Coplanar and skew lines, shortest distance between two lines to practice offline. It includes additional chapter-level practice questions.

Cartesian and vector equation of a plane

Subtopic

Cartesian and vector equation of a plane under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    What is the reflection of the point (1,2,−1)(1, 2, -1) in the plane z=0z = 0?

    A.

    (1,2,1)(1, 2, 1)

    B.

    (1,2,0)(1, 2, 0)

    C.

    (−1,−2,1)(-1, -2, 1)

    D.

    (1,2,−1)(1, 2, -1)

  2. 2.

    The direction cosines of the normal to the plane x+y+z=1x + y + z = 1 are:

    A.

    (13,13,13)(\frac{1}{\sqrt{3}}, \frac{1}{\sqrt{3}}, \frac{1}{\sqrt{3}})

    B.

    (1,1,1)(1, 1, 1)

    C.

    (13,13,13)(\frac{1}{3}, \frac{1}{3}, \frac{1}{3})

    D.

    (0,0,1)(0, 0, 1)

  3. 3.

    If a plane is parallel to the yzyz-plane, its equation is of the form:

    A.

    x=dx = d

    B.

    y=dy = d

    C.

    z=dz = d

    D.

    y+z=dy + z = d

Download the worksheet for Three Dimensional Geometry - Cartesian and vector equation of a plane to practice offline. It includes additional chapter-level practice questions.

Angle between two lines, two planes, a line and a plane

Subtopic

Angle between two lines, two planes, a line and a plane under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    Find the angle between the line x2=y2=z1\frac{x}{2} = \frac{y}{2} = \frac{z}{1} and the line x−54=y−21=z−38\frac{x-5}{4} = \frac{y-2}{1} = \frac{z-3}{8}.

    A.

    cos⁡−1(23)\cos^{-1}(\frac{2}{3})

    B.

    cos⁡−1(1827)\cos^{-1}(\frac{18}{27})

    C.

    cos⁡−1(2027)\cos^{-1}(\frac{20}{27})

    D.

    cos⁡−1(2527)\cos^{-1}(\frac{25}{27})

  2. 2.

    If a line makes angles α,β,γ\alpha, \beta, \gamma with the coordinate axes, then cos⁡2α+cos⁡2β+cos⁡2γ=\cos^2 \alpha + \cos^2 \beta + \cos^2 \gamma =

    A.

    00

    B.

    11

    C.

    22

    D.

    33

  3. 3.

    The direction ratios of two lines are (1,1,0)(1, 1, 0) and (1,2,1)(1, 2, 1). The angle between them is:

    A.

    cos⁡−1(32)\cos^{-1}(\frac{\sqrt{3}}{2})

    B.

    cos⁡−1(23)\cos^{-1}(\frac{\sqrt{2}}{3})

    C.

    cos⁡−1(323)\cos^{-1}(\frac{3}{2\sqrt{3}})

    D.

    cos⁡−1(34)\cos^{-1}(\frac{\sqrt{3}}{4})

Download the worksheet for Three Dimensional Geometry - Angle between two lines, two planes, a line and a plane to practice offline. It includes additional chapter-level practice questions.

Distance of a point from a plane

Subtopic

Distance of a point from a plane under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    The distance of the point (3,4,5)(3, 4, 5) from the plane 2x+y−2z=52x + y - 2z = 5 is:

    A.

    5/35/3

    B.

    3

    C.

    5

    D.

    1/31/3

  2. 2.

    The distance of the point (1,−1,1)(1, -1, 1) from the plane r⃗⋅(2i^−2j^+k^)+5=0\vec{r} \cdot (2\hat{i} - 2\hat{j} + \hat{k}) + 5 = 0 is:

    A.

    1

    B.

    2

    C.

    3

    D.

    4

  3. 3.

    Find the distance of the point (2,3,−5)(2, 3, -5) from the plane x+2y−2z=9x + 2y - 2z = 9.

    A.

    3

    B.

    1

    C.

    0

    D.

    2

Download the worksheet for Three Dimensional Geometry - Distance of a point from a plane to practice offline. It includes additional chapter-level practice questions.

Direction cosines of a line passing through two points

Subtopic

Direction cosines of a line passing through two points under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    Find the direction cosines of the line passing through origin and the point (1,1,0)(1, 1, 0).

    A.

    (12,12,0)(\frac{1}{\sqrt{2}}, \frac{1}{\sqrt{2}}, 0)

    B.

    (1,1,0)(1, 1, 0)

    C.

    (12,12,0)(\frac{1}{2}, \frac{1}{2}, 0)

    D.

    (0,0,1)(0, 0, 1)

  2. 2.

    The direction cosines of a line joining origin to (a,b,c)(a, b, c) are proportional to:

    A.

    (a,b,c)(a, b, c)

    B.

    (1a,1b,1c)(\frac{1}{a}, \frac{1}{b}, \frac{1}{c})

    C.

    (a2,b2,c2)(a^2, b^2, c^2)

    D.

    (a,b,c)(\sqrt{a}, \sqrt{b}, \sqrt{c})

  3. 3.

    If the direction ratios of a line are (1,2,2)(1, 2, 2), what are its direction cosines?

    A.

    (13,23,23)(\frac{1}{3}, \frac{2}{3}, \frac{2}{3})

    B.

    (13,23,23)(\frac{1}{\sqrt{3}}, \frac{2}{\sqrt{3}}, \frac{2}{\sqrt{3}})

    C.

    (1,2,2)(1, 2, 2)

    D.

    (19,29,29)(\frac{1}{9}, \frac{2}{9}, \frac{2}{9})

Download the worksheet for Three Dimensional Geometry - Direction cosines of a line passing through two points to practice offline. It includes additional chapter-level practice questions.

Equation of a Line in Space

Subtopic

Equation of a Line in Space under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    What are the direction ratios of the line perpendicular to the plane 2x−3y+4z=52x - 3y + 4z = 5?

    A.

    (2,−3,4)(2, -3, 4)

    B.

    (2,3,4)(2, 3, 4)

    C.

    (25,−35,45)(\frac{2}{5}, \frac{-3}{5}, \frac{4}{5})

    D.

    (1,1,1)(1, 1, 1)

  2. 2.

    If the lines x−1−3=y−22p=z−32\frac{x-1}{-3} = \frac{y-2}{2p} = \frac{z-3}{2} and x−13p=y−11=z−6−5\frac{x-1}{3p} = \frac{y-1}{1} = \frac{z-6}{-5} are perpendicular, find pp.

    A.

    −107\frac{-10}{7}

    B.

    107\frac{10}{7}

    C.

    710\frac{7}{10}

    D.

    −2-2

  3. 3.

    The Cartesian equation of a line is x−53=y+47=z−62\frac{x-5}{3} = \frac{y+4}{7} = \frac{z-6}{2}. Find its vector form.

    A.

    r⃗=(5i^−4j^+6k^)+λ(3i^+7j^+2k^)\vec{r} = (5\hat{i} - 4\hat{j} + 6\hat{k}) + \lambda(3\hat{i} + 7\hat{j} + 2\hat{k})

    B.

    r⃗=(3i^+7j^+2k^)+λ(5i^−4j^+6k^)\vec{r} = (3\hat{i} + 7\hat{j} + 2\hat{k}) + \lambda(5\hat{i} - 4\hat{j} + 6\hat{k})

    C.

    r⃗=(5i^+4j^+6k^)+λ(3i^+7j^+2k^)\vec{r} = (5\hat{i} + 4\hat{j} + 6\hat{k}) + \lambda(3\hat{i} + 7\hat{j} + 2\hat{k})

    D.

    r⃗=(−5i^+4j^−6k^)+λ(3i^+7j^+2k^)\vec{r} = (-5\hat{i} + 4\hat{j} - 6\hat{k}) + \lambda(3\hat{i} + 7\hat{j} + 2\hat{k})

Download the worksheet for Three Dimensional Geometry - Equation of a Line in Space to practice offline. It includes additional chapter-level practice questions.

Equation of a line through a given point and parallel to a given vector

Subtopic

Equation of a line through a given point and parallel to a given vector under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    A line is parallel to the vector 2i^−j^+3k^2\hat{i} - \hat{j} + 3\hat{k} and passes through the origin. Its Cartesian equation is:

    A.

    x2=y−1=z3\frac{x}{2} = \frac{y}{-1} = \frac{z}{3}

    B.

    x−20=y+10=z−30\frac{x-2}{0} = \frac{y+1}{0} = \frac{z-3}{0}

    C.

    x1=y2=z3\frac{x}{1} = \frac{y}{2} = \frac{z}{3}

    D.

    x−22=y+1−1=z−33\frac{x-2}{2} = \frac{y+1}{-1} = \frac{z-3}{3}

  2. 2.

    Convert the Cartesian equation x−21=y+32=z−53\frac{x-2}{1} = \frac{y+3}{2} = \frac{z-5}{3} to vector form.

    A.

    r⃗=(2i^−3j^+5k^)+λ(i^+2j^+3k^)\vec{r} = (2\hat{i} - 3\hat{j} + 5\hat{k}) + \lambda(\hat{i} + 2\hat{j} + 3\hat{k})

    B.

    r⃗=(−2i^+3j^−5k^)+λ(i^+2j^+3k^)\vec{r} = (-2\hat{i} + 3\hat{j} - 5\hat{k}) + \lambda(\hat{i} + 2\hat{j} + 3\hat{k})

    C.

    r⃗=(i^+2j^+3k^)+λ(2i^−3j^+5k^)\vec{r} = (\hat{i} + 2\hat{j} + 3\hat{k}) + \lambda(2\hat{i} - 3\hat{j} + 5\hat{k})

    D.

    r⃗=(2i^+3j^+5k^)+λ(i^−2j^−3k^)\vec{r} = (2\hat{i} + 3\hat{j} + 5\hat{k}) + \lambda(\hat{i} - 2\hat{j} - 3\hat{k})

  3. 3.

    Find the vector equation of a line passing through (5,2,−4)(5, 2, -4) and having direction ratios (3,2,−8)(3, 2, -8).

    A.

    r⃗=(5i^+2j^−4k^)+λ(3i^+2j^−8k^)\vec{r} = (5\hat{i} + 2\hat{j} - 4\hat{k}) + \lambda(3\hat{i} + 2\hat{j} - 8\hat{k})

    B.

    r⃗=(3i^+2j^−8k^)+λ(5i^+2j^−4k^)\vec{r} = (3\hat{i} + 2\hat{j} - 8\hat{k}) + \lambda(5\hat{i} + 2\hat{j} - 4\hat{k})

    C.

    r⃗=(5i^−2j^+4k^)+λ(3i^−2j^+8k^)\vec{r} = (5\hat{i} - 2\hat{j} + 4\hat{k}) + \lambda(3\hat{i} - 2\hat{j} + 8\hat{k})

    D.

    r⃗=(5i^+2j^+4k^)+λ(3i^+2j^+8k^)\vec{r} = (5\hat{i} + 2\hat{j} + 4\hat{k}) + \lambda(3\hat{i} + 2\hat{j} + 8\hat{k})

Download the worksheet for Three Dimensional Geometry - Equation of a line through a given point and parallel to a given vector to practice offline. It includes additional chapter-level practice questions.

Distance between two skew lines

Subtopic

Distance between two skew lines under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    Find the distance between the lines x1=y0=z0\frac{x}{1} = \frac{y}{0} = \frac{z}{0} and x0=y1=z0\frac{x}{0} = \frac{y}{1} = \frac{z}{0}.

    A.

    1

    B.

    0

    C.

    2\sqrt{2}

    D.

    Undefined

  2. 2.

    Which of the following represents the numerator of the distance formula between two skew lines?

    A.

    Volume of the parallelepiped formed by a2⃗−a1⃗\vec{a_2}-\vec{a_1}, b1⃗\vec{b_1}, b2⃗\vec{b_2}

    B.

    Area of the triangle formed by the lines

    C.

    Sum of direction ratios

    D.

    Dot product of direction vectors

  3. 3.

    If lines r⃗=a1⃗+λb1⃗\vec{r} = \vec{a_1} + \lambda \vec{b_1} and r⃗=a2⃗+μb2⃗\vec{r} = \vec{a_2} + \mu \vec{b_2} are skew, then (a2⃗−a1⃗)⋅(b1⃗×b2⃗)(\vec{a_2}-\vec{a_1}) \cdot (\vec{b_1} \times \vec{b_2}) must be:

    A.

    Zero

    B.

    Non-zero

    C.

    One

    D.

    Infinite

Download the worksheet for Three Dimensional Geometry - Distance between two skew lines to practice offline. It includes additional chapter-level practice questions.

Distance between parallel lines

Subtopic

Distance between parallel lines under Three Dimensional Geometry for Grade 12 CBSE.

About Topic & Revision

Preview questions (no answers)

  1. 1.

    Find the distance between the two parallel lines given by the vector equations: L1:r⃗=(i^+2j^−4k^)+λ(2i^+3j^+6k^)L_1: \vec{r} = (\hat{i} + 2\hat{j} - 4\hat{k}) + \lambda(2\hat{i} + 3\hat{j} + 6\hat{k}) and L2:r⃗=(3i^+3j^−5k^)+μ(2i^+3j^+6k^)L_2: \vec{r} = (3\hat{i} + 3\hat{j} - 5\hat{k}) + \mu(2\hat{i} + 3\hat{j} + 6\hat{k}).

    A.

    2937\frac{\sqrt{293}}{7}

    B.

    29349\frac{\sqrt{293}}{49}

    C.

    2937\frac{293}{7}

    D.

    1717\frac{\sqrt{171}}{7}

  2. 2.

    Find the distance between the lines r⃗=(i^+2j^+k^)+λ(i^+j^+k^)\vec{r} = (\hat{i} + 2\hat{j} + \hat{k}) + \lambda(\hat{i} + \hat{j} + \hat{k}) and r⃗=(i^+2j^+2k^)+μ(i^+j^+k^)\vec{r} = (\hat{i} + 2\hat{j} + 2\hat{k}) + \mu(\hat{i} + \hat{j} + \hat{k}).

    A.

    2/3\sqrt{2/3}

    B.

    1/3\sqrt{1/3}

    C.

    2/32/3

    D.

    1/31/3

  3. 3.

    If two lines are parallel and the vector joining a point on each is a⃗=2i^+j^+2k^\vec{a} = 2\hat{i} + \hat{j} + 2\hat{k} and the direction vector is b⃗=i^+j^\vec{b} = \hat{i} + \hat{j}, find the distance between them.

    A.

    3/23/\sqrt{2}

    B.

    1/21/\sqrt{2}

    C.

    2/22/\sqrt{2}

    D.

    2\sqrt{2}

Download the worksheet for Three Dimensional Geometry - Distance between parallel lines to practice offline. It includes additional chapter-level practice questions.