Introduction to Euclid's Geometry
Every proof in geometry stands on a few statements accepted without proof. Chapter 5, Introduction to Euclid's Geometry, of the NCERT Mathematics textbook for Class 9 presents the axioms and postulates Euclid laid down, from things equal to the same thing being equal to each other, to the famous fifth postulate about parallel lines. You will see how theorems grow from these small beginnings and study equivalent versions of the fifth postulate. The chapter shows what an axiomatic system is and why mathematicians trust it.
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