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References to 'contradiction'
1. $e^r$ is irrational for $r\in\mathbb{Q}\setminus\{0\}$ by Cosmin
2. a line segment has at most one midpoint by Mathprof
3. a space is compact iff any family of closed sets having fip has non-empty intersection by CWoo
4. abelian group is divisible if and only if it is an injective object by joking
5. affine combination by CWoo
6. all bases for a vector space have the same cardinality by CWoo
7. analytic continuation by rspuzio
8. axiomatic geometry by CWoo
9. biquadratic field by Wkbj79
10. bounded linear functionals on $L^p(\mu)$ by azdbacks4234
11. Brouwerian lattice by CWoo
12. Burnside's Theorem by rm50
13. characterization of prime ideals by GrafZahl
14. circle has one center by Wkbj79
15. class number divisibility in extensions by alozano
16. colorings of plane graphs by marijke
17. connectedness is preserved under a continuous map by drini
18. continuous almost everywhere versus equal to a continuous function almost everywhere by Wkbj79
19. contradictory statement by pahio
20. converse of Darboux's theorem (analysis) is not true by Gorkem
21. convex subgroup by CWoo
22. countable algebraic sets by rspuzio
23. defect theorem by Ziosilvio
24. dimension formulae for vector spaces by yark
25. e is transcendental by pahio
26. Eisenstein criterion by Daume
27. Eisenstein criterion in terms of divisor theory by pahio
28. equivalent definitions for UFD by joking
29. every map into sphere which is not onto is nullhomotopic by joking
30. every ordered field with the least upper bound property is isomorphic to $\mathbb{R}$, proof that by mps
31. example of a connected space that is not path-connected by yark
32. example of algebras and coalgebras which cannot be turned into Hopf algebras by joking
33. example of false implies true by Algeboy
34. example of free module by mathcam
35. extension of a poset by CWoo
36. face of a convex set by CWoo
37. field extension with Galois group $Q_8$ by rm50
38. finite field cannot be algebraically closed by rspuzio
39. free modules over a ring which is not a PID by joking
40. generalized quaternion group by Algeboy
41. high school mathematics by matte
42. in a vector space, $\lambda v = 0$ if and only if $\lambda =0$ or $v$ is the zero vector by aoh45
43. incidence geometry by CWoo
44. induction by Daume
45. injective $C^*$-algebra homomorphism is isometric by asteroid
46. integer contraharmonic means by pahio
47. Lasker-Noether theorem by CWoo
48. lattice ideal by CWoo
49. least and greatest zero by pahio
50. martingale proof of the Radon-Nikodym theorem by gel
51. mathematics vocabulary by matte
52. maximum flow/minimum cut theorem by bbukh
53. metric spaces are Hausdorff by waj
54. modus tollens by rspuzio
55. numerable set by juanman
56. ordered vector space by CWoo
57. ordinal space by CWoo
58. ping-pong lemma by uriw
59. positive cone by CWoo
60. prime harmonic series by Cosmin
61. primitive element of biquadratic field by Wkbj79
62. proof by PrimeFan
63. proof of AAA (hyperbolic) by Wkbj79
64. proof of Banach fixed point theorem by asteroid
65. proof of casus irreducibilis for real fields by rm50
66. proof of characterization of connected compact metric spaces. by paolini
67. proof of characterizations of the Jacobson radical by rspuzio
68. proof of De l'H\^opital's rule by paolini
69. proof of exhaustion by compact sets for $\mathbb{R}^n$ by cvalente
70. proof of existence and uniqueness of best approximations by asteroid
71. proof of fundamental theorem of algebra by scanez
72. proof of Hahn-Banach theorem by paolini
73. proof of Lindemann-Weierstrass theorem and that e and $\pi$ are transcendental by rm50
74. proof of properties of Hopfian and co-Hopfian groups by joking
75. proof of Scott-Wiegold conjecture by whm22
76. proof of simplicity of Mathieu groups by monster
77. proof of Vizing's theorem (for graphs) by marijke
78. proof of Wilson's theorem by Cosmin
79. proof that $n^2-n+41$ is prime for $0\leq n\leq 40$ by rm50
80. proof that $\sqrt{2}$ is irrational by Wkbj79
81. proof that a domain is Dedekind if its ideals are invertible by gel
82. proof that a domain is Dedekind if its ideals are products of maximals by gel
83. proof that a Noetherian domain is Dedekind if it is locally a PID by gel
84. proof that a path connected space is connected by n3o
85. proof that there are infinitely many primes using the Mersenne primes by PrimeFan
86. properties of injective functions by rspuzio
87. properties of spanning sets by CWoo
88. properties of well-ordered sets by GrafZahl
89. proposed elementary proof of Fermat's last theorem by Mathprof
90. pumping lemma (context-free languages) by rspuzio
91. pumping lemma (regular languages) by rspuzio
92. quadratic fields that are not isomorphic by Wkbj79
93. quotient group of a topological group by its identity component is totally disconnected by joking
94. Ramsey-theoretic proof of the Erd\H{o}s-Szekeres theorem by mps
95. rational and irrational by pahio
96. scattered space by CWoo
97. Scott continuous by CWoo
98. separated uniform space by CWoo
99. sets that do not have an infimum by sleske
100. Sikorski's extension theorem by CWoo
101. sinc is not $L^1$ by cvalente
102. SL(n;R) is connected by Stephaninos
103. spectrum is a non-empty compact set by asteroid
104. square root by Wkbj79
105. subgroups of $S_4$ by rm50
106. subsemigroup of a cyclic semigroup by CWoo
107. sum of $\frac{\mu(n)}{n}$ by mathcam
108. surjective open maps in terms of nets by asteroid
109. techniques in mathematical proofs by CWoo
110. terms from foreign languages used in mathematics (html version) by Wkbj79
111. terms from foreign languages used in mathematics (page images version) by Wkbj79
112. the real numbers are indecomposable as a topological space by joking
113. there are an infinite number of primes $\equiv 1\mod m$ by rm50
114. Tutte theorem by scineram
115. Zariski lemma by polarbear