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Any two things that can be shown to coincide with each other are equal.Equal things having equal things subtracted from them have equal remainders.Equal things having equal things added to them remain equal.Two things that are equal to a third are equal to each other.The five "common notions" of Euclid have application in every branch of mathematics, they are: Given a point and a line not containing the point, there is one and only one parallel to the line through the point.A circle is uniquely defined by its center and a point on its circumference.The five postulates of Euclid that pertain to geometry are specific assumptions about lines, angles, and other geometric concepts.
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Euclid based his geometry on five postulates and five "common notions," of which the postulates are assumptions specific to geometry, and the "common no tions" are completely general axioms. Euclidean geometry provides a classic example. Postulate is synonymous with axiom, though sometimes axiom is taken to mean an assumption that applies to all branches of mathematics, in which case a postulate is taken to be an assumption specific to a given theory or branch of mathematics. In this way, an entire branch of mathematics can be built up from a few postulates.
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Once a theorem has been proven it is may be used in the proof of other theorems.
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Postulates are the fundamental propositions used to prove other statements known as theorems. A postulate is an assumption, that is, a proposition or statement, that is assumed to be true without any proof.
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