Introduction To Euclidean Geometry

Euclidean geometry (or Euclid’s geometry) is the study of geometry (especially for the shapes of geometrical figures) which is attributed to the Alexandrian mathematician Euclid who has explained in his book on geometry known as Elements.

Euclid has introduced the geometry fundamentals in his book elements and has stated 5 main axioms or postulates. Here, we will look into the details of this topic’s concepts and understand what his postulates or axioms were. The key points covered in this lesson are:

  • History of Euclidean Geometry
  • Euclid’s Elements
  • Euclid’s Postulates
  • Euclid’s Axioms
  • Euclidean Geometry Worksheet

History of Euclidean Geometry

The excavations at Harappa and Mohenjo-Daro depict the extremely well-planned towns of Indus Valley Civilization (about 3300-1300 BC). The flawless construction of Pyramids by the Egyptians is yet another example of extensive use of geometrical techniques used by the people back then. In India, the Sulba Sutras, textbooks on Geometry depict that the Indian Vedic Period had a tradition of Geometry.

The development of geometry was taking place gradually, when Euclid, a teacher of mathematics, at Alexandria in Egypt, collected most of these evolutions in geometry and compiled it into his famous treatise, which he named ‘Elements’.

Euclid’s Elements

Euclid’s Elements is a mathematical and geometrical work consisting of 13 books written by ancient Greek mathematician Euclid in Alexandria, Ptolemaic Egypt. Further, the ‘Elements’ was divided into thirteen books which popularized geometry all over the world. As a whole, these Elements is a collection of definitions, postulates (axioms), propositions (theorems and constructions), and mathematical proofs of the propositions.

Book 1 to 4th and 6th discuss plane geometry. He gave five postulates for plane geometry known as Euclid’s Postulates and the geometry is known as Euclidean geometry. It was through his works, we have a collective source for learning geometry; it lays the foundation for geometry as we know now.

Euclid’s Postulates

Before discussing Euclid’s Postulates let us discuss a few terms as listed by Euclid in his book 1 of the ‘Elements’. The postulated statements of these are:

  • Assume the three steps from solids to points as solids-surface-lines-points. In each step, one dimension is lost.
  • A solid has 3 dimensions, the surface has 2, the line has 1 and point is dimensionless.
  • A point is anything that has no part, a breadthless length is a line and the ends of a line point.
  • A surface is something which has length and breadth only.

It can be seen that the definition of a few terms needs extra specification. Now let us discuss these Postulates in detail.

Euclid’s Postulate 1:

A straight line can be drawn from any one point to another point.

This postulate states that at least one straight line passes through two distinct points but he did not mention that there cannot be more than one such line. Although throughout his work he has assumed there exists only a unique line passing through two points.

Euclid’s Geometry Postulate 1

Euclid’s Postulate 2:

A terminated line can be further produced indefinitely.

In simple words what we call a line segment was defined as a terminated line by Euclid. Therefore this postulate means that we can extend a terminated line or a line segment in either direction to form a line. In the figure given below, the line segment AB can be extended as shown to form a line.

Euclid’s Postulate 2

Euclid’s Postulate 3:

A circle can be drawn with any centre and any radius.

Any circle can be drawn from the end or start point of a circle and the diameter of the circle will be the length of the line segment.

Euclid’s Postulate 4:

All right angles are equal to one another.

All the right angles (i.e. angles whose measure is 90°) are always congruent to each other i.e. they are equal irrespective of the length of the sides or their orientations.

Euclid’s Postulate 5:

If a straight line falling on two other straight lines makes the interior angles on the same side of it taken together less than two right angles, then the two straight lines, if produced indefinitely, meet on the side on which the sum of angles is less than two right angles.

Read More: Euclid’s Fifth Postulate

Further, these Postulates and axioms were used by him to prove other geometrical concepts using deductive reasoning. No doubt the foundation of present-day geometry was laid by him and his book the ‘Elements’.

Euclidean Geometry Axioms

  1. Things are equal to one another if those things are equal to the same thing.
  2. The wholes are equal if equals are added to equals.
  3. The remainders are equal if equals are subtracted from equals.
  4. Things are equal to one another if they coincide with one another.
  5. The whole will be greater than the part.

Euclidean Geometry Worksheet

  1. How many dimensions do solids, points and surfaces have?
  2. What is the shape of a pyramid’s base?
  3. If a + b =10 and a = c, then prove that c + b =10.
  4. Can two distinct intersecting line be parallel to each other at the same time? Justify.
  5. Read the following sentence and mention which of Euclid’s axiom is followed: “X’s salary is equal to Y’s salary. Due to the recession, the salaries of X and y are reduced to half. Now the final salary of X will still be equal to Y.”

More Topics on Euclidean Geometry

So here we had a detailed discussion about Euclidean geometry and postulates. Keep visiting BYJU’S to get more such maths topics explained in an easy way. Also, register now and access numerous video lessons on different maths concepts.


Practise This Question

The angle which is less than 90 is known as