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01
LESSON 01 · CLASS 9 MATHEMATICS (NCERT)

Geometric Definitions & Euclid's Axioms

Understand undefined terms (point, line, plane), definitions, and Euclid's 7 fundamental axioms of logic and geometry.

01 · AXIOMS vs POSTULATES

What are Axioms and Postulates?

• Axioms: Basic truths assumed without proof used throughout mathematics.
• Postulates: Assumptions specific to geometry.

EUCLID'S 7 AXIOMS

Euclid's Common Notions

1. Things which are equal to the same thing are equal to one another (If A = B and B = C ⟹ A = C).

2. If equals are added to equals, the wholes are equal.

3. If equals are subtracted from equals, the remainders are equal.

4. Things which coincide with one another are equal to one another.

5. The whole is greater than the part (If A = B + C where C > 0 ⟹ A > B).

6. Things which are double of the same things are equal to one another.

7. Things which are halves of the same things are equal to one another.