Lines – Definition, Types, & Examples
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 90o 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
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