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  2. Intercept theorem - Wikipedia

    en.wikipedia.org/wiki/Intercept_theorem

    The converse of the theorem implies that a homothety transforms a line in a parallel line. Conversely, the direct statement of the intercept theorem implies that a geometric transformation is always a homothety of center O, if it fixes the lines passing through O and transforms every other line into a parallel line.

  3. Thales's theorem - Wikipedia

    en.wikipedia.org/wiki/Thales's_theorem

    In geometry, Thales's theorem states that if A, B, and C are distinct points on a circle where the line AC is a diameter, the angle ∠ ABC is a right angle. Thales's theorem is a special case of the inscribed angle theorem and is mentioned and proved as part of the 31st proposition in the third book of Euclid 's Elements . [ 1 ]

  4. Converse (logic) - Wikipedia

    en.wikipedia.org/wiki/Converse_(logic)

    The converse may or may not be true, and even if true, the proof may be difficult. For example, the four-vertex theorem was proved in 1912, but its converse was proved only in 1997. [3] In practice, when determining the converse of a mathematical theorem, aspects of the antecedent may be taken as establishing context.

  5. Converse theorem - Wikipedia

    en.wikipedia.org/wiki/Converse_theorem

    In the mathematical theory of automorphic forms, a converse theorem gives sufficient conditions for a Dirichlet series to be the Mellin transform of a modular form. More generally a converse theorem states that a representation of an algebraic group over the adeles is automorphic whenever the L-functions of various twists of it are well-behaved.

  6. Converse relation - Wikipedia

    en.wikipedia.org/wiki/Converse_relation

    The converse relation does satisfy the (weaker) axioms of a semigroup with involution: () = and () =. [12] Since one may generally consider relations between different sets (which form a category rather than a monoid, namely the category of relations Rel ), in this context the converse relation conforms to the axioms of a dagger category (aka ...

  7. Midpoint theorem (triangle) - Wikipedia

    en.wikipedia.org/wiki/Midpoint_theorem_(triangle)

    The midpoint theorem generalizes to the intercept theorem, where rather than using midpoints, both sides are partitioned in the same ratio. [1] [2] The converse of the theorem is true as well. That is if a line is drawn through the midpoint of triangle side parallel to another triangle side then the line will bisect the third side of the triangle.

  8. Conway base 13 function - Wikipedia

    en.wikipedia.org/wiki/Conway_base_13_function

    The Conway base 13 function is a function created by British mathematician John H. Conway as a counterexample to the converse of the intermediate value theorem.In other words, it is a function that satisfies a particular intermediate-value property — on any interval (,), the function takes every value between () and () — but is not continuous.

  9. Borel–Cantelli lemma - Wikipedia

    en.wikipedia.org/wiki/Borel–Cantelli_lemma

    A related result, sometimes called the second Borel–Cantelli lemma, is a partial converse of the first Borel–Cantelli lemma. The lemma states: If the events E n are independent and the sum of the probabilities of the E n diverges to infinity, then the probability that infinitely many of them occur is 1.