# Visual calculus > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Visual_calculus > Markdown URL: https://mediated.wiki/source/Visual_calculus.md > Source: https://en.wikipedia.org/wiki/Visual_calculus > Source revision: 1351022331 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Visual mathematical proofs}} {{Use mdy dates|date=July 2020}} thumb|right|300px|Mamikon's theorem - the areas of the tangent clusters are equal. Here, the original curve with the tangents drawn from it is a semicircle. '''Visual calculus''', invented by [Mamikon Mnatsakanian](/source/Mamikon_Mnatsakanian) (known as Mamikon), is an approach to solving a variety of [integral calculus](/source/Integral) problems.[http://www.cco.caltech.edu/~mamikon/calculus.html Visual Calculus] Mamikon Mnatsakanian Many problems that would otherwise seem quite difficult yield to the method with hardly a line of calculation. Mamikon collaborated with [Tom Apostol](/source/Tom_Apostol) on the 2013 book ''New Horizons in Geometry'' describing the subject. ==Description== thumb|upright|Illustration of Mamikon's method showing that the areas of two annuli with the same chord length are the same regardless of inner and outer radii.{{cite book|title=The Edge of the Universe: Celebrating Ten Years of Math Horizons|isbn = 9780883855553|url=https://books.google.com/books?id=I9oVP8TlyqIC&pg=PA70|access-date=9 May 2017|last1 = Haunsperger|first1 = Deanna|last2 = Kennedy|first2 = Stephen|year = 2006}} Mamikon devised his method in 1959 while an undergraduate, first applying it to a well-known geometry problem: find the area of a ring ([annulus](/source/annulus_(mathematics))), given the length of a [chord](/source/Chord_(geometry)) tangent to the inner circumference. Perhaps surprisingly, no additional information is needed; the solution does not depend on the ring's inner and outer dimensions. The traditional approach involves algebra and application of the [Pythagorean theorem](/source/Pythagorean_theorem). Mamikon's method, however, envisions an alternate construction of the ring: first the inner circle alone is drawn, then a constant-length tangent is made to travel along its circumference, "sweeping out" the ring as it goes. Now if all the (constant-length) tangents used in constructing the ring are translated so that their points of tangency coincide, the result is a circular disk of known radius (and easily computed area). Indeed, since the inner circle's radius is irrelevant, one could just as well have started with a circle of radius zero (a point)—and sweeping out a ring around a circle of zero radius is indistinguishable from simply rotating a [line segment](/source/line_segment) about one of its endpoints and sweeping out a disk. Mamikon's insight was to recognize the equivalence of the two constructions; and because they are equivalent, they yield equal areas. Moreover, the two starting curves need not be circular—a finding not easily proven by more traditional geometric methods. This yields '''Mamikon's theorem''': :''The area of a tangent sweep is equal to the area of its tangent cluster, regardless of the shape of the original curve.'' ==Applications== ===Area of a cycloid=== [[File:Mamikon Cycloid.svg|thumb|right|300px|Finding the area of a [cycloid](/source/cycloid) using Mamikon's theorem.]] The area of a [cycloid](/source/cycloid) can be calculated by considering the area between it and an enclosing rectangle. These tangents can all be clustered to form a circle. If the circle generating the cycloid has radius {{math|''r''}} then this circle also has radius {{math|''r''}} and area {{math|π''r''2}}. The area of the rectangle is {{math|2''r'' × 2π''r'' {{=}} 4π''r''2}}. Therefore, the area of the cycloid is {{math|3π''r''2}}: it is 3 times the area of the generating circle. The tangent cluster can be seen to be a circle because the cycloid is generated by a circle and the tangent to the cycloid will be at [right angle](/source/right_angle) to the line from the generating point to the rolling point. Thus the tangent and the line to the contact point form a right-angled triangle in the generating circle. This means that clustered together the tangents will describe the shape of the generating circle.{{cite book |last1=Apostol, Mnatsakanian |title=New Horizons in Geometry |date=2012 |publisher=Mathematical Association of America |isbn=9781614442103 |doi=10.5948/9781614442103|doi-broken-date=July 1, 2025 }} == See also == * [Cavalieri's principle](/source/Cavalieri's_principle) * [Hodograph](/source/Hodograph) – This is a related construct that maps the velocity of a point using a polar diagram. * ''[The Method of Mechanical Theorems](/source/The_Method_of_Mechanical_Theorems)'' * [Pappus's centroid theorem](/source/Pappus's_centroid_theorem) * [Planimeter](/source/Planimeter) * [Tristan Needham](/source/Tristan_Needham)'s visual complex analysis. == References == {{reflist}} == External links == * [https://www.its.caltech.edu/~mamikon/ ProjMath Mamikon] * [https://mathworld.wolfram.com/ProofwithoutWords.html Proof without Words] from [MathWorld](/source/MathWorld) *[https://demonstrations.wolfram.com/MamikonsMethodForTheAreaOfTheCycloid/ Wolfram Interactive Demonstration of Mamikon's theorem] Category:Calculus Category:Geometry Category:Integrals Category:Proof without words --- Adapted from the Wikipedia article [Visual calculus](https://en.wikipedia.org/wiki/Visual_calculus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Visual_calculus?action=history)). 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