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From Ruiyuan Chen
The Archimedean property, density of Q, every real number is a supremum of rationals -
From Ruiyuan Chen
Dedekind-completeness, equivalence with dual condition for infima, characterization of R as unique-up-to-unique-isomorphism Dedekind-complete ordered field -
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From Ruiyuan Chen
Ordered rings and fields, basic consequences of axioms, Q is the smallest ordered field up to isomorphism -
From Ruiyuan Chen
Lack of square roots in Q, preview of connection between square roots and limits & definition of limits via ordering -
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From Ruiyuan Chen
Descent of functions to quotient sets, descent of multi-variable functions, quotient structures and congruence relations -
From Ruiyuan Chen
Correspondence between equivalence relations, partitions, and surjections; integers mod d -
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From Ruiyuan Chen
Relational substructures vs induced substructures, homomorphisms, bijective homomorphisms vs isomorphisms -
From Ruiyuan Chen
Digraphs, reflexivity, symmetry, transitivity, antisymmetry, trichotomy, preorders, partial orders, total orders, equivalence relations -
From Ruiyuan Chen
The fundamental theorem of arithmetic as a monoid isomorphism, transport of properties and constructions along isomorphisms -
From Ruiyuan Chen
Isomorphisms, vs bijective homomorphisms, exponential isomorphism between addition and multiplication -
From Ruiyuan Chen
Image and preimage as monoid homomorphisms, image and preimage of substructures under homomorphisms -
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From Ruiyuan Chen
Subgroups, intersections and generated subgroups, powers of elements in groups, generated subgroups in Z and gcd's -
From Ruiyuan Chen
Left and right inverses in monoids, groups, group of invertible elements in a monoid -
From Ruiyuan Chen
Submonoids, intersection of submonoids, submonoid generated by a subset, submonoids and equational axioms -
From Ruiyuan Chen
(Commutative) monoids, numeric and set examples, functions under composition, free monoids -
From Ruiyuan Chen
Euclidean division with remainder, greatest common divisors, coprime integers, the Euclidean algorithm and Bézout's identity -
From Ruiyuan Chen
Binomial coefficients, symmetry, Pascal's triangle, Pascal's identity, diagonal sums of Pascal's triangle, the binomial theorem, row sums of Pascal's… -
From Ruiyuan Chen
Set-theoretic definition of N and successor, the axiom of infinity, definition of arithmetic, preview of construction of Z, Q, R