Just Imagine!!! You are living in a twodimensional plane, and in this world has no height. You could still travel around, visit your friends. You could measure distances and angles. You could move fast or slow. You could go forward and backward or sideways. You could move in straight lines, circles, or anything so long as you never go up or down. What would be your life like living in two dimensions plane? Well, for me it's impossible to imagine. And that is the reason why Three Dimension Geometry is important and necessary to learn their properties. In the real world, everything you see is in a threedimensional shape, it has length, breadth, and height. Just simply look around and observe. Even a thin sheet of paper has some thickness.
The next time you play a mobile game like PUBG, thank threedimension geometry for the realistic look to the landscape and the characters that inhabit the game’s virtual world.
Applications of geometry in the real world include the computeraided design (CAD) for construction blueprints, the design of assembly systems in manufacturing such as automobiles, nanotechnology, computer graphics, visual graphs, video game programming, and virtual reality creation. Geometry plays a very important role in calculating the location of galaxies, solar systems, planets, stars, satellites and other moving bodies in space. Geometry helps in calculations between coordinates also help to chart a trajectory for a space vehicle’s journey and its entry point into a planet’s atmosphere.
The Tesla Roadster in space An animation tracking the orbit of Musk’s Tesla Roadster
That’s why it is necessary to learn threedimension geometry their properties.
Coordinate of a point in space, distance formula
Direction cosine and Direction ratio
The angle between two intersecting lines
Skew lines and the shortest distance between two lines
Equation of line and plane
The intersection of line and plane
The position of a point in twodimension (2D) is given by two numbers P(x, y) but in threedimension geometry, the position of a point P is given by three numbers P(x, y, z). Three mutually perpendicular lines intersect at one point, the point O(0, 0, 0) is known as the origin in the space. These three mutually perpendicular lines form three planes namely XY, YZ, ZX called coordinate planes.
Coordinate of a Point in Space, Distance Formula
are unit vectors along OX, OY, and OZ respectively. Point P(x, y, z) be any point in the space. Then, the position vector of a point is given by .
The distance between two points in the space and is given by .
Direction Cosine and Direction Ratio
If and are the angle which a vector OP makes with the positive direction of the coordinate axis OX, OY and OZ respectively. Then and are known as Direction Cosine of vector OP and denoted by 'l', 'm', and 'n' respectively.
Let 'l', 'm', and 'n' are Direction Cosine of a vector 'r' and 'a', 'b', and 'c' be three number such that 'a', 'b', and 'c' are proportional to 'l', 'm', and 'n'
Then, (a,b,c) are direction ratios.
Equation of a Straight Line in Space
Vector Equation of a Line Passing Through a Given Point and Parallel to Given Vector 'A' is any given point, 'BC' is the given line and 'AP' is parallel to given line 'BC'. Then, the equation of a line parallel to a given vector 'BC'and passing through a point 'A' is given by . (Where .
Angle Between Two Lines
The equation of two straight lines in space is given as \(r=a+\lambda b\) and \(r=a'+\mu b'\). Then, the angle between the two lines is .
If the equations of lines are in cartesian form, . Then, the angle between the two lines is given as .
Skew lines and the shortest distance between two lines
In space, if two lines intersect, then the shortest distance between them is zero. Also, if two lines are parallel in space, then the shortest distance between them is perpendicular distance. Further, there are such lines in space which are neither intersecting nor parallel. Such pair of lines are noncoplanar and known as skew lines.
The shortest distance between two skew lines and is
In cartesian form, equation of two skew lines are .
Then, the shortest distance between them is
.
Equation of Plane
A plane is a surface such that if any two points are taken on it, the line segment joining these two points lies completely on the surface.
Equation of plane in Normal form
The vector equation of a plane normal to a unit vector and at a distance d from the origin is given by .
To get the equation of the plane in cartesian form. let P(x, y, z) be any point on the plane then, position vector . let l, m and n be the direction cosine of .
Then,
From the vector equation of the plane
This is the cartesian equation of the plane in normal form.
Intercept form of a Plane
The equation of a plane having intercepting lengths a, b and c with Xaxis, Yaxis and Zaxis respectively is given by .
The important formulas of Three Dimension Geometry
As soon as you are done with the concepts and numerical you must do the previous year’s questions. With the previous year questions, you would totally understand where you are lacking and you will be able to improve accordingly.
Take online mock test regularly in a timebound manner to increase your speed and accuracy. This activity will particularly help you in JEE Mains.
Know your strength and weakness and try to improve both.
While practicing if you feel that any question which appears to be important then make a note of that. Later while revising this chapter, you must solve that question again, this will help you to brush up your concepts.
You must create small formula notebook/flashcards for this chapter and then revise them on a weekly basis to keep them in your mind always.
Maths NCERT Books are one of the most important study material as this book covers all the topics. Start from NCERT book, the example given in NCERT is simple and lucid. Most of the important concepts and theory you will understand by simply solving those given example. And also solve all problems (including miscellaneous problem) of NCERT. If you do this, your basic level of preparation will be completed.
Then you can refer to the books Vectors & 3D Geometry by Amit M. Agarwal, Cengage Mathematics Vectors & 3D Geometry or RD Sharma. 3D Geometry explained very beautifully in the book Arihant Algebra and there are lots of questions with crystal clear concepts. But again the choice of reference book depends on you, find the book that best suits you the best depending on how well you are clear with the concepts and the difficulty of the questions you require. Rather than referring all the books just stick to one good book but for practicing more problem you can refer to other books.
Chapters 
Chapters Name 
Chapter 1 

Chapter 2 

Chapter 3 

Chapter 4 

Chapter 5 

Chapter 6 

Chapter 7 

Chapter 8 

Chapter 9 

Chapter 10 

Chapter 12 

Chapter 13 

Chapter 14 

Chapter 15 

Chapter 16 
The coordinates of the foot of the perpendicular from the point (1, −2, 1) on the plane containing the lines
and
is
(2, −4, 2)
(−1, 2, −1)
(0, 0, 0)
(1, 1, 1)
The distance of the point (1, 3, −7) from the plane passing through the point (1, −1, −1), having normal perpendicular
to both the lines and is:
The shortest distance between the lines
and
lies in the interval :
[0, 1)
[1, 2)
(2, 3]
(3, 4]