• The Mathematical Education
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• v.53 no.1
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• pp.41-55
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• 2014

In recent years, there has been increasing interest in the pedagogical importance of counter-examples that contradict statements about mathematics education research and the curriculum revision process for high school mathematics courses. Using a literature research method, this study analyzed views about counter-examples according to a method of approach to statements and the classification of counter-examples and their criteria. The study also described the learnability of the content of counter-examples presented in Korean secondary school mathematics textbooks. The results showed that generating many counter-examples enables learners to understand mathematical concepts exactly, construct links between mathematical contents, and have flexible thoughts about mathematical objects. Considering the learnability of counter-examples, the contents of counter-examples in school mathematics textbooks are needed for mathematics teachers and students to generate numerous counter-examples and verify the justification of generating counter-examples in various manners.

• Journal for History of Mathematics
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• v.26 no.5_6
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• pp.401-416
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• 2013

There has been increasing interest in recent years in the pedagogical importance of counter-examples that focuses on pedagogical perspectives. But there is no research that undergraduate students' generating counter-examples and proposing the true statements. This study analyze 6 undergraduate students' response to interview tasks and the process of their generating counter-examples and proposing true statements. The results of interviews are that the more undergraduate students generate various counter-examples, the more valid they propose true statements. If undergraduate students have invalid understanding of logical implication and generate only one counter-example, they would not propose true statements that modify the given statement, preserving the antecedent. In pre-service teacher's education and school mathematics class, we need to develop materials and textbooks about counter-examples and false statements.

• School Mathematics
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• v.15 no.4
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• pp.743-758
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• 2013

This paper analyses the examples of polygons taken in the 1st grade middle school mathematics textbooks. We analysed generic examples, non-examples and counter-examples represented in these textbooks. And also we classified and analysed with examples of the concept and the application of a procedure. We analysed the differences of methods among these textbooks representing the same concepts or procedures. The findings from the analysis showed that these textbooks mostly make use of generic examples. The examples of concept and procedure vary depending upon the textbooks. Also, many textbooks haven't properly represented various positions and figures of polygons. Textbooks need to represent various and appropriate examples in order to expand the example space of the students.

• Journal of Educational Research in Mathematics
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• v.21 no.4
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• pp.379-398
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• 2011

In learning environment at mathematics education, prove and refute are essential abilities to demonstrate whether and why a statement is true or false. Learning proofs and counter examples within the domain of limit of sequence is important because preservice teacher encounter limit of sequence in many mathematics courses. Recently, a number of studies have showed evidence that pre service and students have problem with mathematical proofs but many research studies have focused on abilities to produce proofs and counter examples in domain of limit of sequence. The aim of this study is to contribute to research on preservice teachers' productions of proofs and counter examples, as participants showed difficulty in writing these proposition. More importantly, the analysis provides insight and understanding into the design of curriculum and instruction that may improve preservice teachers' learning in mathematics courses.

• Journal of the Korean Data and Information Science Society
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• v.16 no.4
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• pp.1013-1015
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• 2005

Liu[Fuzzy Optimization and Decision Making, 2(2003), 87-100] proved that convergence in credibility does not imply convergence a.s. and convergence in mean does not imply convergence a.s. by giving counter-examples. But these examples are not true. In this note, we prove that convergence in credibility implies convergence a.s. and convergence in mean implies convergence a.s.

• The Pure and Applied Mathematics
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• v.27 no.1
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• pp.1-11
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• 2020

In this paper we determine conditions which a function a(t) must satisfy to insure that the function a'(t) is an element of the separable Hilbert space L²_a,b[0, T]. We then proceed to illustrate our results with several pertinent examples and counter-examples.

• East Asian mathematical journal
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• v.23 no.2
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• pp.159-174
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• 2007

In this paper, the concepts of pairwise fuzzy $G_{\delta}$-connected spaces and pairwise fuzzy $G_{\delta}$-extremally disconnected spaces are introduced. The concept of pairwise fuzzy $G_{\delta}$-basically disconnected spaces is defined. Characterizations of the above spaces are given besides giving several examples. Interrelations among the spaces introduced are discussed and some relevant counter examples are given.

• Journal of applied mathematics & informatics
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• v.34 no.3_4
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• pp.355-357
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• 2016

Recently, some results of Blackwell's Theorem in which interarrival times are characterized as fuzzy variables under t-norm-based fuzzy operations are discussed by Hong. However, these results are invalid. In this note, we give counter examples of these results.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.1277-1280
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• 1993

In this short note we show that a number of conclusions unacceptable to our intuitions or commonsense knowledge can be drawn from Zadeh's possiliblity theory.

• Journal of applied mathematics & informatics
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• v.38 no.5_6
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• pp.533-545
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• 2020

We initiate and introduce the notion of binary soft mapping, which is defined on collection of binary soft sets named as binary soft class over two initial universes U₁ and U₂ with fixed set of parameters. We also define and study the properties of binary soft images and binary soft inverse images of binary soft sets. Examples and counter examples are also given in support of presented properties. Moreover, these concepts are applied to the problem of medical diagnosis in medical expert systems.