Examples exist of mathematically correct results derived by incorrect lines of reasoning. Such an argument, however true the conclusion appears to … 展开

Mathematical analysis as the mathematical study of change and limits can lead to mathematical fallacies — if the properties of integrals and 展开

Many functions do not have a unique inverse. For instance, while squaring a number gives a unique value, there are two possible square roots of a positive number. The square root is multivalued. One value can be chosen by convention as the 展开

Many mathematical fallacies in geometry arise from using an additive equality involving oriented quantities (such as adding vectors along a given line or adding oriented angles in the plane) to a valid identity, but which fixes only the absolute value of (one … 展开

There exist several fallacious proofs by induction in which one of the components, basis case or inductive step, is incorrect. Intuitively, proofs by induction work by arguing that if a statement is true in one case, it is true in the next case, and hence by repeatedly applying … 展开

• Anomalous cancellation – Kind of arithmetic error
• Division by zero – Class of mathematical expression
• List of incomplete proofs
• Mathematical coincidence – Coincidence in … 展开

• Invalid proofs at Cut-the-knot (including literature references)
• Classic fallacies with some discussion
• More invalid proofs from AhaJokes.com
• Math jokes including an invalid proof 展开