-
CBSE Important Questions›
-
CBSE Previous Year Question Papers›
- CBSE Previous Year Question Papers
- CBSE Previous Year Question Papers Class 12
- CBSE Previous Year Question Papers Class 10
-
CBSE Revision Notes›
-
CBSE Syllabus›
-
CBSE Extra Questions›
-
CBSE Sample Papers›
- CBSE Sample Papers
- CBSE Sample Question Papers For Class 5
- CBSE Sample Question Papers For Class 4
- CBSE Sample Question Papers For Class 3
- CBSE Sample Question Papers For Class 2
- CBSE Sample Question Papers For Class 1
- CBSE Sample Question Papers For Class 12
- CBSE Sample Question Papers For Class 11
- CBSE Sample Question Papers For Class 10
- CBSE Sample Question Papers For Class 9
- CBSE Sample Question Papers For Class 8
- CBSE Sample Question Papers For Class 7
- CBSE Sample Question Papers For Class 6
-
ISC & ICSE Syllabus›
-
ICSE Question Paper›
- ICSE Question Paper
- ISC Class 12 Question Paper
- ICSE Class 10 Question Paper
-
ICSE Sample Question Papers›
- ICSE Sample Question Papers
- ISC Sample Question Papers For Class 12
- ISC Sample Question Papers For Class 11
- ICSE Sample Question Papers For Class 10
- ICSE Sample Question Papers For Class 9
- ICSE Sample Question Papers For Class 8
- ICSE Sample Question Papers For Class 7
- ICSE Sample Question Papers For Class 6
-
ICSE Revision Notes›
- ICSE Revision Notes
- ICSE Class 9 Revision Notes
- ICSE Class 10 Revision Notes
-
ICSE Important Questions›
-
Maharashtra board›
-
Rajasthan-Board›
- Rajasthan-Board
-
Andhrapradesh Board›
- Andhrapradesh Board
- AP Board Sample Question Paper
- AP Board syllabus
- AP Board Previous Year Question Paper
-
Telangana Board›
-
Tamilnadu Board›
-
NCERT Solutions Class 12›
- NCERT Solutions Class 12
- NCERT Solutions Class 12 Economics
- NCERT Solutions Class 12 English
- NCERT Solutions Class 12 Hindi
- NCERT Solutions Class 12 Maths
- NCERT Solutions Class 12 Physics
- NCERT Solutions Class 12 Accountancy
- NCERT Solutions Class 12 Biology
- NCERT Solutions Class 12 Chemistry
- NCERT Solutions Class 12 Commerce
-
NCERT Solutions Class 10›
-
NCERT Solutions Class 11›
- NCERT Solutions Class 11
- NCERT Solutions Class 11 Statistics
- NCERT Solutions Class 11 Accountancy
- NCERT Solutions Class 11 Biology
- NCERT Solutions Class 11 Chemistry
- NCERT Solutions Class 11 Commerce
- NCERT Solutions Class 11 English
- NCERT Solutions Class 11 Hindi
- NCERT Solutions Class 11 Maths
- NCERT Solutions Class 11 Physics
-
NCERT Solutions Class 9›
-
NCERT Solutions Class 8›
-
NCERT Solutions Class 7›
-
NCERT Solutions Class 6›
-
NCERT Solutions Class 5›
- NCERT Solutions Class 5
- NCERT Solutions Class 5 EVS
- NCERT Solutions Class 5 English
- NCERT Solutions Class 5 Maths
-
NCERT Solutions Class 4›
-
NCERT Solutions Class 3›
-
NCERT Solutions Class 2›
- NCERT Solutions Class 2
- NCERT Solutions Class 2 Hindi
- NCERT Solutions Class 2 Maths
- NCERT Solutions Class 2 English
-
NCERT Solutions Class 1›
- NCERT Solutions Class 1
- NCERT Solutions Class 1 English
- NCERT Solutions Class 1 Hindi
- NCERT Solutions Class 1 Maths
-
JEE Main Question Papers›
-
JEE Main Syllabus›
- JEE Main Syllabus
- JEE Main Chemistry Syllabus
- JEE Main Maths Syllabus
- JEE Main Physics Syllabus
-
JEE Main Questions›
- JEE Main Questions
- JEE Main Maths Questions
- JEE Main Physics Questions
- JEE Main Chemistry Questions
-
JEE Main Mock Test›
- JEE Main Mock Test
-
JEE Main Revision Notes›
- JEE Main Revision Notes
-
JEE Main Sample Papers›
- JEE Main Sample Papers
-
JEE Advanced Question Papers›
-
JEE Advanced Syllabus›
- JEE Advanced Syllabus
-
JEE Advanced Mock Test›
- JEE Advanced Mock Test
-
JEE Advanced Questions›
- JEE Advanced Questions
- JEE Advanced Chemistry Questions
- JEE Advanced Maths Questions
- JEE Advanced Physics Questions
-
JEE Advanced Sample Papers›
- JEE Advanced Sample Papers
-
NEET Eligibility Criteria›
- NEET Eligibility Criteria
-
NEET Question Papers›
-
NEET Sample Papers›
- NEET Sample Papers
-
NEET Syllabus›
-
NEET Mock Test›
- NEET Mock Test
-
NCERT Books Class 9›
- NCERT Books Class 9
-
NCERT Books Class 8›
- NCERT Books Class 8
-
NCERT Books Class 7›
- NCERT Books Class 7
-
NCERT Books Class 6›
- NCERT Books Class 6
-
NCERT Books Class 5›
- NCERT Books Class 5
-
NCERT Books Class 4›
- NCERT Books Class 4
-
NCERT Books Class 3›
- NCERT Books Class 3
-
NCERT Books Class 2›
- NCERT Books Class 2
-
NCERT Books Class 1›
- NCERT Books Class 1
-
NCERT Books Class 12›
- NCERT Books Class 12
-
NCERT Books Class 11›
- NCERT Books Class 11
-
NCERT Books Class 10›
- NCERT Books Class 10
-
Chemistry Full Forms›
- Chemistry Full Forms
-
Biology Full Forms›
- Biology Full Forms
-
Physics Full Forms›
- Physics Full Forms
-
Educational Full Form›
- Educational Full Form
-
Examination Full Forms›
- Examination Full Forms
-
Algebra Formulas›
- Algebra Formulas
-
Chemistry Formulas›
- Chemistry Formulas
-
Geometry Formulas›
- Geometry Formulas
-
Math Formulas›
- Math Formulas
-
Physics Formulas›
- Physics Formulas
-
Trigonometry Formulas›
- Trigonometry Formulas
-
CUET Admit Card›
- CUET Admit Card
-
CUET Application Form›
- CUET Application Form
-
CUET Counselling›
- CUET Counselling
-
CUET Cutoff›
- CUET Cutoff
-
CUET Previous Year Question Papers›
- CUET Previous Year Question Papers
-
CUET Results›
- CUET Results
-
CUET Sample Papers›
- CUET Sample Papers
-
CUET Syllabus›
- CUET Syllabus
-
CUET Eligibility Criteria›
- CUET Eligibility Criteria
-
CUET Exam Centers›
- CUET Exam Centers
-
CUET Exam Dates›
- CUET Exam Dates
-
CUET Exam Pattern›
- CUET Exam Pattern
Important Questions For CBSE Class 12 Mathematics Chapter 11 – Three Dimensional Geometry
Three-dimensional geometry is an important part of analytical geometry. In this chapter, students learn to use vector algebra in geometric equations. Important Questions Class 12 Mathematics Chapter 11 covers all the concepts of three-dimensional geometry, including the direction cosine and direction ratios of a line joining two points, the angle between two lines, the angle between a line and a plane, etc. Students must revise these concepts several times and practise more questions to be able to solve questions quickly in the exam. Subject matter experts have carefully selected Class 12 Mathematics Chapter 11 Important Questions after consulting the updated CBSE Syllabus and questions from the past years. Students will get an idea of what kind of questions they can expect in the exam and what marks those questions will have.
CBSE Class 12 Mathematics Chapter-11 Important Questions
Study Important Questions For Class 12 Mathematics Chapter 11- Three Dimensional Geometry
Given below is a sample set of the Important Questions Class 12 Mathematics Chapter 11. For the full set, students can access the link provided here.
Very Short Answer Questions (1 Mark)
Q.1. P is a point located on a three-dimensional plane. What is the distance between P from the x-axis? The coordinate of P is (a, b, c).
Ans. The distance of point P from the x-axis is a unit.
Q.2. A line while passing through a three-dimensional plane makes an angle α,β,γ with x, y, and z axes respectively. Find the value of + + .
Ans. If a line makes an angle α, β, γ with the coordinate axes, then the value of
+ + = 1.
Therefore,
3 − + + = 1
Or, + + = 2
Q.3. Convert the vector into the cartesian form: r = i–j + λ2j–k.
Ans. The cartesian form of r = i–j + λ2j–k is x-12= y+10= z-0-1
Q.4. Find the distance between the planes 2x + 2y – z + 2 = 0 and 4x + 4y – 2z + 5 = 0.
Ans. The equations of the given planes are,
2x + 2y – z + 2 = 0 …………….(i)
4x + 4y – 2z + 5 = 0 ……………….(ii)
Equation (ii) can be written as 2x + 2y – z +52 = 0
Therefore, the two planes are parallel to each other.
The distance between the two parallel planes = 2- 5222 + 22 + 12 = 16 unit.
Q.5. Prove the following planes are parallel to each other.
x + y – 2z + 4 = 0; 3x + 3y – 6z + 5 = 0.
Ans. The given planes are,
x + y – 2z + 4 = 0 ………. (i)
3x + 3y – 6z + 5 = 0
Or, x + y – 2z + 53 = 0 ……….. (ii)
Therefore, the planes do not intersect each other. Hence, they are parallel to each other.
Q.6. Find the coordinates of P when the value of OP is 3 with the direction ratios proportional to -1, 2, 3, where O is the origin.
Ans. The equation of the line OP is,
x-1= y2= z-2
Let, x-1= y2= z-2 = k
Therefore, x = -k; y = 2k; z = -2k
Again, the distance of OP = 3 (given)
Therefore, k2 + 2k2 + 2k2 = 3
Or, 9k2 = 3
Or, k = ± 3
The coordinate of k = (∓1, ±2, ∓2).
Short Answer Questions (4 Mark)
Q.1. Three points A (0, −1, −1), B (−4, 4, 4), and C (4,5,1) are in the same plane. Find the equation of the plane containing all the three points.
Ans. The required equation for the plane containing the points A, B, and C is,
x-0 y+1 z+1 -4 4 4 4 5 1 = 0
⟹4x – 5y + 9z +3=0
Q.2. The direction cosines of two mutually perpendicular lines are l1, m1, n1 and l2, m2, n2. Prove that, the direction cosines of the line perpendicular on both lines are m1n2−n1m2, n1l2−l1n2, l1m2−m1l2.
Ans. The vector equation of the perpendicular line is,
i j k l1 m1 n1 l2 m2 n2 = (m1n2−n1m2) i+ (n1l2−l1n2) j+ (l1m2−m1l2)k
Therefore, the directional cosines are (m1n2−n1m2) i, (n1l2−l1n2) j, (l1m2−m1l2)k.
Q.3. A line PQ x-41= 2y-42= k-z-2= a passes through the plane 2x – 4y + z = 7. What is the value of K?
Ans. Since the line PQ x-41= 2y-42= k-z-2= a lies in the given plane 2x – 4y + z = 7, the value of a becomes 0.
Therefore,
x-41=0 ; or, x = 4
y = 2; z = k
Putting the values of x, y, and z in the equation of the plane we get,
2*4 – 4*2 + k = 7
Or, k = 7
The value of k, therefore, is 7.
Q.4. Find equation of the plane through line of intersection of planes r . 2i+6j + 12 = 0 and r . 3i–j + 4k = 0 which is at unit distance from the origin.
Ans. r . 2i+6j + 12 = 0
The cartesian form of the equation is x + 3y + 6 = 0 ……….(i)
r . 3i–j + 4k = 0 can be expressed as 3x – y + 4z =0 in the cartesian form ……. (ii)
Direction ratio of the plane perpendicular to the planes is
i j k 1 3 0 3 -1 4 = 12i − 4j − 10k
The intersecting line of the lines x + 3y + 6 = 0 and 3x – y + 4z =0 is
x1=3x+6-1=-(6z+3)5
Let, the equation of required plane is ax + by + cz = d
Therefore, it can be said that, 12i − 4j − 10k =d
0, -2, -2 lies on that plane.
Putting the values, we get,
12(0) − 4(−2) − 10(−2) = d
Or, d = 28
Therefore, the final equation becomes,
12x – 4y – 10z = 28
Or, 6x – 2y – 5z = 14
Q.5. Two points -2, 4, -5 and 1, 2, 3are located on a certain line. Find the direction cosines of the line passing through these points.
Ans. Let the points are P and Q.
Position of P = -2, 4, -5
Position of Q = 1, 2, 3
Formula of direction cosines is, x2–x1PQ, y2–y1PQ, z2–z1PQ
PQ is the distance between the two points.
Therefore, PQ = x2–x12+y2–y12+ z2–z12
Or, PQ = 1-(-2)2+2-42+ 3-(-5)2
Or, PQ = 9+4+64
Or, PQ = 77
Putting the values in cosines’ formula we get,
x2–x1PQ, y2–y1PQ, z2–z1PQ
= 1-(-2)77, 2-477, 3-(-5)77
=377, -277, 877
Therefore, the required direction cosines are 377, -277, 877 .
Long Answer Questions (6 Mark)
Q.1. Find the shortest distance between the two lines given below.
x-83=y+9-16=z-107 and x-153=y-298=z-55
Ans. The given equations are,
x-83 = y+9 -16= z-107 ……………. (i)
x-153 = y-298 = z-55 ……………….. (ii)
From the first equation we get,
The line passes through the point (8, -9, 10).
Its directional ratio is proportional to <3, -16, 7>
Therefore, the vector equation is, r = a1 + b1
Where, a1 = 8i − 9j + 10k
From the second equation we get,
The line passes through (15, 29, 5).
Its direction ratio is proportional to (3, 8, -5).
The vector equation will be r = a2 + b2
Where, a2 = 15i + 29j + 5k
b2 = 3i + 8j − 5k
Therefore, a2 – a1 = 15i + 29j + 5k − 8i + 9j − 10k
Or, a2 – a1 = 7i + 38j − 5k ………… (iii)
b2 × b1 = i j k 3 -16 7 3 8 -5
= (80 − 56)i − (−15 − 21)j + (24 + 48)k
= 24i + 36j + 72k ……………… (iv)
a2 – a1 . b2 × b1 = 7i + 38j – 5k . 24i + 386 + 72k
= 168+1368−360
=1176
b2 × b1 = 242+362+722 (from (iv))
= 7056
= 84
We know that, the shortest distance between two lines is a2 – a1 . b2 × b1 b2 × b1
By putting the values, we get
a2 – a1 . b2 × b1 b2 × b1 = 117684
= 14
Therefore, the shortest distance between the two lines will be 14 units.
Q.2. A variable plane is at a constant distance 3p from the origin and meets the axes at A, B, and C points. If the centroid of ∆ABC is (α, β, γ) then prove that 12 + 12 + 12 = 1p2 .
Ans. Let the equation of the plane is a + b + c = 1, where a, b, c are the intercepts of the plane and α, , are axes.
The distance between the origin and the plane is
1-2+-2+-2 = 3p
Or, -2+-2+-2 = 19p2
The coordinate of a centroid of a triangle in a three dimensional plane is (a3, b3, c3).
The given coordinate is (α, β, γ).
Therefore, a = 3 ; b = 3, c = 3.
By substituting the values of a, b, and c, we get,
192 + 192 + 192 = 19p2
Therefore, 12 + 12 + 12 = 1p2 [proved].
Q.3. Find the angle between the two lines passing through a three-D plane.
x+33=y-15=z+34 ; x+11=y-41=z-52
Ans. x+33=y-15=z+34 ………… (i)
The direction ratio (a1, b1, c1) = (3, 5, 4)
x+11=y-41=z-52 …………….. (ii)
The direction ratio (a2, b2, c2) = (1, 1, 2)
The cosine between two lines is
cos = a1a2+ b1b2+ c1c2a12+ b12+ c122a22+ b22+ c22
= 3.1+ 5.1+ 4.232+ 52+ 4212+ 12+ 22
= 1650 6
= 1652 32
=853
The required angle = 853
Q.4. A perpendicular is drawn from point P 2i– j+5k is on the line r = 11i-2j-8k+ λ10i-4j-11k. Find the length and the foot of the perpendicular.
Ans. Let, the foot of the perpendicular = L.
The position vector of L = 11i− 2j −8k + λ(10i− 4j− 11k)
= (11+10λ) i + (−2−4λ) j + (−8−11λ) k ……….. (i)
The length of PL is equal to the difference of position vector P and position vector L.
Therefore PL = (11 +10λ)i+ (−2−4λ) j + (−8−11λ) k − (2i−j+5k)
= (9+10λ) i + (−1−4λ) j + (−13−11λ) k ……….. (ii)
Since PL is perpendicular to the given line and the given line is parallel to b = 10i-4j-11k
PL.b = 0
Therefore,
(9+10) i + (-1-4) j + (-13-11) k . 10i-4j-11k = 0
⟹ 10(9+10λ) − 4(−1−4λ) − 11(−13−11λ) = 0
⟹237λ = −237
⟹ λ = −1
Placing the value of in equation (i) we get,
i+ 2j+ 3k
Therefore, the foot of the perpendicular is i+ 2j+ 3k
Now,
PL = i+ 2j+ 3k– 2i– j+ 5k
= −i+3j-2k
So, the length of the perpendicular
PL = 1+9+4 = 14 unit.
Q.1 Find the angle between the two planes 3x-6y+2z-7 = 0 and 2x+2y-2z = 5.
Option:
Ans.
Q.2
Ans.
Q.3
Option:
Ans.
Q.4
Option:
Ans.
Q.5
Option:
Ans.
Please register to view this section
FAQs (Frequently Asked Questions)
1. Why is three-dimensional geometry important?
In our daily lives, whatever objects we see are mostly three-dimensional. For example, chairs, tables, books, stationery objects like pens and pencils, etc. So, when we study mathematics as a discipline and learn measurement of common objects in mensuration, trigonometry, and geometry, we should also learn measurement related to three-dimensional geometry. Again, three-dimensional geometry is a crucial part of analytical geometry. This chapter is also important from the perspective of the board exam. Therefore, students must prepare the chapter very well for a better performance in exams.
2. Why should students practise Chapter 11 Class 12 Mathematics Important Questions?
Students must learn to solve questions quickly. The more questions they solve, the more skilled they become at calculation. By solving the important questions, students will get a fair idea of the question pattern, the types of questions that are important from an exam perspective, and thus they will feel more confident. So, students should practise more questions before the exam.
3. How will Important Questions provided by Extramarks benefit students?
Mathematics Class 12 Chapter 11 Important Questions provided by Extramarks are prepared after consulting the past years’ Important Questions and the CBSE Syllabus. The question set is divided into three sections: questions carrying 1 mark, 4 marks, and 6 marks. The solutions are also provided along with the questions. So, students can focus on solving questions instead of collecting questions from every possible source.