**Key Concepts**

- Lines
- Classification of Triangles
- Classification of Quadrilaterals

**Lines**

**Introduction: **

**Definition**

**Line:**

A line is a figure formed when two points are connected with minimum distance between them and have no ends on both sides.

A line *AB* is represented by

AB↔

A real-life example of a line

**Line Segment:**

A line segment is part of a line that has a fixed endpoint on both the ends.

A line segment *AB* is represented by AB−

A real-life example of a line segment

**Ray:**

A ray is a part of a line that has only one fixed point, and the other point does not have any end.

A line segment *AB* is represented by AB→

A real-life example of a ray

**Types of lines:**

Basically, lines are of 3 types:

- Parallel lines

- Intersecting lines

- Perpendicular lines

**Parallel lines**

Two lines are said to be parallel lines if they lie in the same plane and never meet.

*Parallel lines*

*Non- Parallel lines*

A real-life example of parallel lines

**Intersecting lines**

If two lines meet at a point, they are said to be intersecting lines.

A real-life example of intersecting lines

Scissors, the two blades of the scissors intersect at each other to make it work effectively.

**Perpendicular lines**

When two lines intersect at an angle of 90^{o }or at a right angle, then they are perpendicular to each other.

A real-life example of perpendicular lines

Clocks are the best examples to show perpendicular lines at 3 O’ clock and 9 O’ clock.

**Classification of Triangles**

**Triangle (Definition)**

A triangle is a closed shape with three angles, three sides and three vertices.

Triangles can be classified as:

- On the basis of angles
- On the basis of measurement of their sides

A real-life example of triangles

**Classification of Quadrilaterals**

**Quadrilateral**

A quadrilateral is a closed two-dimensional shape that has 4 sides, 4 angles, and 4 vertices.

A real-life example of a quadrilateral

**Types of Quadrilaterals:**

Quadrilaterals are classified based on their sides, angles, and diagonals.

A real-life example of types of quadrilaterals

**Exercise:**

- Find out the number of sleeping lines, slanting lines, curved lines, circles, square, triangle and rectangle in the figure below:

- Is it possible to have an obtuse acute triangle? Explain.
- What is true about all quadrilaterals?
- What is the difference between a square, and a rhombus?
- Can a trapezoid have perpendicular sides?
- Classify each triangle by its sides, and then by its angles.
- The blades of an open pair of scissors look like what pair of lines?
- What geometric term could you use to describe the top, and bottom edges of a book?
- How many acute angles are there in an equilateral triangle?
- What kinds of triangles never have right angles?

**What we have learnt:**

- Recognize and define lines, line segments and rays
- Understand parallel and perpendicular lines
- Understand triangles based on angles
- Understand triangles based on sides
- Learn quadrilaterals and classification of quadrilaterals
- Solve questions based on lines, angles, and shapes

**Concept Map:**

**Classification of Lines**

**Classification of Quadrilaterals**

**Classification of Triangles**

#### Related topics

#### Addition and Multiplication Using Counters & Bar-Diagrams

Introduction: We can find the solution to the word problem by solving it. Here, in this topic, we can use 3 methods to find the solution. 1. Add using counters 2. Use factors to get the product 3. Write equations to find the unknown. Addition Equation: 8+8+8 =? Multiplication equation: 3×8=? Example 1: Andrew has […]

Read More >>#### Dilation: Definitions, Characteristics, and Similarities

Understanding Dilation A dilation is a transformation that produces an image that is of the same shape and different sizes. Dilation that creates a larger image is called enlargement. Describing Dilation Dilation of Scale Factor 2 The following figure undergoes a dilation with a scale factor of 2 giving an image A’ (2, 4), B’ […]

Read More >>#### How to Write and Interpret Numerical Expressions?

Write numerical expressions What is the Meaning of Numerical Expression? A numerical expression is a combination of numbers and integers using basic operations such as addition, subtraction, multiplication, or division. The word PEMDAS stands for: P → Parentheses E → Exponents M → Multiplication D → Division A → Addition S → Subtraction Some examples […]

Read More >>#### System of Linear Inequalities and Equations

Introduction: Systems of Linear Inequalities: A system of linear inequalities is a set of two or more linear inequalities in the same variables. The following example illustrates this, y < x + 2…………..Inequality 1 y ≥ 2x − 1…………Inequality 2 Solution of a System of Linear Inequalities: A solution of a system of linear inequalities […]

Read More >>
Comments: