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Chapter 11

Three Dimensional Geometry

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Class 12 of 3d Geometry discusses the concept of three-dimensional geometry while also providing an overview and review of two-dimensional analytical geometry. This chapter uses Cartesian techniques to describe three-dimensional geometry. The basic principles of vectors and how to utilise vector algebra to solve issues related to three-dimensional geometry are also covered in this chapter. Topics covered in this Chapter: 1. Introduction 2. Direction Cosines and Direction Ratios of a Line 3. Equation of a Line Space 4. Angle Between Two Lines 5. Shortest Distance Between Two Lines 6. Plane 7. Coplanarity of Two Lines 8. Angle between two Planes 9. Distance of a Point from a Plane 10. Angle Between a Line and a Plane

Introduction

3d Geometry Class 12 introduces the concept of three-dimensional geometry while giving an overview and revision of analytical geometry in two dimensions. This chapter explains three-dimensional geometry using Cartesian methods. The other topics included in this chapter are the basic concepts of vectors and ways to use vector algebra in solving problems related to three-dimensional geometry. Apart from this, students learn and can practise the concepts of directions and e-direction cosines along with the direction ratios of a line joining two points.

Finally, Three Dimensional Geometry class 12 helps students in learning the equations of lines and planes in space under the following conditions and much more:

  • An angle between two lines
  • An angle between two planes
  • An angle between a line and a plane
  • The shortest distance between two skew lines
  • The distance of a point from a plane

It depends on a two-dimensional plane consisting of the x-axis and the y-axis. Opposite to one another, the axes partition the plane into four areas. Each part is known as a quadrant. There are four quadrants. Namely:-

Quadrant I

Quadrant II

Quadrant III

Quadrant IV

The two-dimensional plane where the 

  • the x-axis is the horizontal axis
  • the y-axis is the vertical axis 

A point in the plane is characterized as an arranged pair (x,y), with the end goal that x is controlled by its flat separation from the beginning, and y is dictated by its vertical separation from the source.

In Three Dimensional Geometry Class 12, students will start off by using an example to understand and notice direction cosines and direction ratios of a line. Furthermore, students will discover why a line in space does not pass through the origin, as well as how to construct a line through the origin and parallel to the given line to obtain its direction cosines.

Students will also examine the relationship between the direction cosines of a line throughout 3d Geometry Class 12 NCERT Solutions. This will need the application of several of the examples provided in this section. The direction cosines of a line travelling through two locations will also be studied. To deeply grasp the concept, students will also need to see the example presented. This section contains numerous examples related to various topics to aid students in understanding complex concepts.

In short, for calculating straight lines, the general equation of a straight line is denoted as y = mx + c, where m is the gradient, and y = c is the value/the point at which the line cuts the y-axis.

In this section, concepts like vectors and cartesian equations of a line in space are explained. Students will explore the uniqueness of a line and determine if it passes through a particular point(s) and direction.

In this chapter, students will also learn how to solve the equation of a line that passes through a given point and is parallel to a specified vector. Aside from that, they will learn how to distinguish between a Cartesian form and a vector form. This section also includes numerous related examples to help students fully grasp this concept. The equation of lines going between two points will next be taught to the students.

When two straight lines intersect, a set of angles are formed. This intersection forms a pair of acute and obtuse angles. The slopes of the intersecting lines determine the absolute values of angles formed as a result of this intersection. Here, an example is given to illustrate the concept of the angle between two lines in three-dimensional geometry. This section involves several theoretical concepts and dives deeply into the examples provided to help students grasp these concepts. Consider two lines denoted by the following equations:

y = m1x + c1 and y = m2x + c2.

Then the angle between these two lines is given by the following formula:

 

  • tan θ = |(m1 – m2)/ (1 + m1m2)|

In this section of Three Dimensional Geometry Class 12 NCERT Solutions, the calculation of the shortest distance between two parallel lines and the fact that it will be the perpendicular distance drawn from a point on one line onto the other line will be covered. Students will learn why the shortest distance between two lines should be joined from one place on one line to one point on the other line in order to obtain the shortest segment. Apart from this, students will also study the reason why for skew lines the line of the shortest distance will be perpendicular to both the lines. In addition to this, there is more content pertaining to the distance between two skew lines and the distance between parallel lines. For all of the above concepts, there are several examples related to these concepts and some in association with other concepts as they will help students understand the concepts better and feel confident during exams. The formula of the shortest distance between two line denoted by D is given by the following formula:

 

D = I c2 - c1 I / ( 1 + m2 )1/2

In this section of Three Dimensional Geometry, planes are explained in terms of:

  • Equations of three dimensional geometry in a standard form
  • Passing through a point perpendicular to a given direction
  • Passing through three given non-collinear points

The topics discussed include the equation of the plane perpendicular to a given vector and passing through a given point, the equation of a plane passing through three non-collinear points, the intercept form of the equation of a plane, and a plane passing through the intersection of two given planes. Several examples are provided in this section to help understand these concepts.

Here, the coplanarity of two lines in three-dimensional geometry is discussed. If there is a geometric plane that encompasses all of the points in space, they are said to be coplanar.

Three points, for example, are considered coplanar if and only if they are distinct and non-collinear. Thus, the plane that they determine is unique.

  • This section contains several theoretical concepts that aid students in understanding the subsequent sections. 

This section defines the angle between two planes as the angle between their normal. This section is followed by several relevant examples to help students understand these concepts and hold on to the definition. 

In this section of Three Dimensional Geometry Class 12 NCERT Solutions, students will compute the distance of a point from a plane both from a vector form as well as Cartesian form. Several examples are provided to illustrate these concepts as they are tricky to understand. The formula is as follows:

 

D = I A (x1 - x0) + B (y1 - y0) + C (z1 - z0) I / (A2 + B2 + C2)½

 

D = I A x1 + B y1 + C z1 I / (A2 + B2 + C2)1/2

In this section, the angle between the line and the plane's normal is defined as the complement of the angle between the line and the plane. A graphic with numerous examples is provided to help you better understand and apply this concept in three-dimensional geometry.

 

The formula is as follows:

Cos θ = I ( [ A1A2 + B1B2 + C1C2 ] / [(A 12 + B 12 + C 12)½ (A 22 + B 22 + C 22)1/2]) I

Students go through every section of this chapter in depth to increase their knowledge and awareness of the subject as this chapter has several applications in many competitive exams. Students will be able to better grasp this chapter provided they go over the NCERT answers for Three-dimensional Geometry 12 as it is prepared by subject experts. They will also learn simple and advanced concepts and theorems. The key features of Three Dimensional Geometry Class 12 NCERT Solutions are the following:

  • Three Dimensional Geometry uses easy language and eye-catching formats.
  • You will most definitely achieve more knowledge about the concepts and theorems cited in NCERT Solutions for Class 12 Maths Chapter 11.
  • Students will learn how to evaluate their knowledge gap and overcome it with the help of the Three Dimensional Geometry Class 12 NCERT Solutions.
  • Students learn how to expand their knowledge in the main sections.
  • Students will be able to comprehend any assignments constructed on the concepts from Three-dimensional Geometry Class 12 Chapter 11.
  • After studying Three Dimensional Geometry, students will not panic when presented with enormous books on the same chapter.
  • Three Dimensional Geometry Class 12 notes are as per guidelines of the CBSE syllabus.
  • The topics are as per the latest syllabus pattern in order to aid the students in revising the notes in minimum time with maximum accuracy. These notes will evidently save the student’s time when they prepare for the exams.


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