Visual calculus

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Mamikon’s theorem – the house of the tangent clusters are equal. Right here the long-established curve with the tangents drawn from it is a semicircle.

Visual calculus, invented by Mamikon Mnatsakanian (identified as Mamikon), is an skill to solving a diversity of integral calculus problems.[1] Many problems that can perchance well in every other case seem pretty fascinating yield to the skill with infrequently a line of calculation, assuredly paying homage to what Martin Gardner known as “aha! solutions” or Roger Nelsen a proof with out phrases.[2][3]


Illustration of Mamikon’s skill showing that the areas of two annuli with the identical chord dimension are the identical in spite of inner and outer radii.[4]

Mamikon devised his skill in 1959 whereas an undergraduate, first applying it to a effectively-identified geometry mission: uncover the house of a hoop (annulus), given the scale of a chord tangent to the inner circumference. Per chance surprisingly, no extra info is wished; the answer doesn’t depend on the ring’s inner and outer dimensions.

The oldschool skill involves algebra and utility of the Pythagorean theorem. Mamikon’s skill, nonetheless, envisions an alternate building of the ring: first the inner circle by myself is drawn, then a fixed-dimension tangent is made to roam alongside its circumference, “sweeping out” the ring because it goes.

Now in case your total (fixed-dimension) tangents aged in setting up the ring are translated so that their factors of tangency coincide, the result is a circular disk of identified radius (and easily computed house). Certainly, since the inner circle’s radius is irrelevant, one would possibly perchance perchance well perchance exact as effectively occupy started with a circle of radius zero (a level)—and sweeping out a hoop around a circle of zero radius is indistinguishable from merely rotating a line section about conception to be one of its endpoints and sweeping out a disk.

Mamikon’s insight was once to acknowledge the equivalence of the 2 constructions; and because they’re a similar, they yield equal areas. Furthermore, the 2 starting up curves needn’t be circular—a finding no longer easily proven by extra oldschool geometric recommendations. This yields Mamikon’s theorem:

The house of a tangent sweep is equal to the house of its tangent cluster, in spite of the shape of the long-established curve.


Space of a cycloid[[edit]

Discovering the house of a cycloid utilizing Mamikon’s theorem.

The house of a cycloid would possibly perchance perchance well perchance also be calculated by brooding about the house between it and an enclosing rectangle. These tangents can all be clustered to invent a circle. If the circle producing the cycloid has radius r then this circle also has radius r and house πr2. The house of the rectangle is 2r × 2πr = 4πr2. Subsequently the house of the cycloid is r2: it is 3 instances the house of the manufacturing circle.

The tangent cluster would possibly perchance perchance well perchance also be seen to be a circle for the explanation that cycloid is generated by a circle and the tangent to the cycloid will seemingly be at exact attitude to the line from the manufacturing divulge the rolling level. Thus the tangent and the line to the contact level invent a exact-angled triangle in the manufacturing circle. This means that clustered collectively the tangents will describe the shape of the manufacturing circle.[5]

Gaze also[[edit]


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