Euclid was a Greek mathematician from Alexandria known as the "Father of Geometry". His influential work Elements laid out the principles of Euclidean geometry through a small set of axioms and deduced many other geometric principles through logical proofs. Elements was used as the main geometry textbook for over 2000 years. Euclid introduced deductive reasoning and the axiomatic method to geometry which established it as the first example of a formal axiomatic system.

1. EUCLID GEOMETRY
MADE BY :- PRATIKSHA MANWATKAR
CLASS – IX/M

2. Who Was Euclid
Euclid, sometimes called Euclid of
Alexandria to distinguish him from Euclid
of Megara, was a Greek mathematician,
often referred to as the "Father of
Geometry". He was active
in Alexandria during the reign
of Ptolemy I (323–283 BC).
His Elements is one of the most influential
works in the history of mathematics,
serving as the main textbook for
teaching mathematics (especially geometr
y) from the time of its publication until the
late 19th or early 20th century. In
the Elements, Euclid deduced the
principles of what is now called Euclidean
geometry from a small set of axioms.
Euclid also wrote works
on perspective, conic sections, spherical
geometry, number theory and rigor

3. Why Was He Famous
• Euclid was the first Greek
mathematician who
initiated a new way of
thinking the study of
geometry.
• He introduced the method
of proving a geometrical
result by deductive
reasoning based upon
previously proved result
and some self evident
specific assumptions
called axioms .

4. Euclidean Geometry
• Euclidean geometry is a mathematical
system attributed to the Alexandrian Greek
mathematician Euclid, which he described
in his textbook on geometry: the Elements.
Euclid's method consists in assuming a
small set of intuitively appealing axioms,
and deducing many
other propositions (theorems) from these.
Although many of Euclid's results had
been stated by earlier
mathematicians,[1] Euclid was the first to
show how these propositions could fit into
a comprehensive deductive and logical
system. TheElements begins with plane
geometry, still taught in secondary
school as the first axiomatic system and
the first examples of formal proof. It goes
on to the solid geometry of three
dimensions. Much of the Elements states
results of what are now
called algebra and number theory,
explained in geometrical language.
•

5. AXIOMS OF EUCLID
• AXIOMS
• Things which are equal to the
same thing are also equal to
one another.
• If equals be added to equals,
the wholes are equal.
• If equals be subtracted from
equals, the remainders are
equal.
• Things which coincide with
one another are equal to one
another.
• The whole is greater than the
part.

6. POSTULATES OF EUCLID
• POSTULATES
• Let the following be postulated:
• To draw a straight line from any
point to any point.
• To produce a finite straight line
continuously in a straight line.
• To describe a circle with any centre
and distance.
• That all right angles are equal to
one another.
• That if a straight line falling on two
straight lines makes the interior
angles on the same side less than
two right angles, the straight lines,
if produced indefinitely, will meet on
that side on which the angles are
less that two right angles.
•

7. EXAMPLES OF AXIOMS
• Suppose the area of a rectangle is equal to the
area of a triangle and the area of that triangle is
equal to the area of a square. By applying
Euclid’s first axiom, we can say that the areas of
the rectangle and the square are equal.
Similarly, if a = b and b = c, then we can also
say that a = c

8. EXAMPLES OF AXIOMS
• Let us now discuss the second axiom. Let
us consider a line segment AD in which,
AB = CD.
• If we add BC to both sides of this relation
(equals are added), then according to
Euclid’s second axiom, we can say that,
AB + BC = CD + BC i.e., AC = BD.
•

9. EXAMPLES OF AXIOMS
• Consider the rectangles ABCD and PQRS drawn in the
given figure.
Suppose that the areas of the rectangles ABCD and PQRS are equal. If
we remove triangle XYZ from each of the two rectangles as shown
in the figure, then we can say that the areas of remaining portions of
the two triangles are equal. We derived this from Euclid’s third
axiom.

10. EXAMPLES OF AXIOMS
• Euclid’s fourth axiom is sometimes used in geometrical proofs. Let us
consider a point Q that lies between points P and R of a line segment PR as
shown in the figure.
• From this figure, we can notice that (PQ + QR) coincides with the line
segment PR. Thus, by using Euclid’s fourth axiom, which states that “things
which coincide with one another are equal to one another”, we can write,
PQ + QR = PR.
• Using the same figure that we used in the fourth axiom, we can see that PQ
is a part of line segment PR. By using Euclid’s fifth axiom, we can say that
the whole i.e., line segment PR is greater than the part i.e., PQ.
Mathematically, we can write it as PR > PQ
•

11. EXAMPLES OF POSTULATES
Postulate one suggests that if we have two points P and Q
on a plane, then we can draw at least one line that can
simultaneously pass through these two points. Euclid
does not mention that only one line can pass through
two points, but he assumes the same. The fact that there
can be only one line passing through two given points is
illustrated in the following figure.

12. EXAMPLES OF POSTULATES
• Postulate 2: A terminated line can be produced
indefinitely.
• This postulate can be considered as an extension of
postulate 1. According to this postulate, we can make a
different straight line from a given line by extending its
points on either sides of the plane.
• In the following figure, MN is the original line, while M′N′
is the new line formed by extending the original line in
either direction.
•

13. EXAMPLES OF POSTULATES
• Postulate 3: It is possible to describe a circle with any centre and
radius.
• According to Euclid, a circle is a plane figure consisting of a set of
points that are equidistant from a reference point. It can be drawn
with the knowledge of its centre and radius.
• The shapes of circles do not change when different radii are
considered. Only their sizes change.
•

14. EXAMPLES OF POSTULATES
• Postulate 4: All right angles are equal to one another.
• A right angle is unique in the sense that it measures
exactly 90°. Hence, all right angles are of the measure
90° irrespective of the lengths of their arms. Hence, all
right angles are equal to each other.
• Remark: Unlike right angles, acute and obtuse angles
are not unique in the sense that their measures lie
between 0° to 89° and 91° to 179° respectively. Hence,
the measure of one acute angle is not the same as the
measure of another acute angle. Similarly, each obtuse
angle has a different measure.