Evangelista Torricelli, a student of Galileo, is remembered as the inventor of the barometer. He was also a talented mathematician and he discovered the remarkable properties of a simple geometric surface, now often called Torricelli’s Trumpet. It is the surface generated when the curve for is rotated in 3-space about the x-axis.
Continue reading ‘Torricelli’s Trumpet & the Painter’s Paradox’
Published March 2, 2017
Tags: Analysis, History, Logic
Children sometimes amuse themselves searching for the biggest number. After trying millions, billions and trillions, they realize that there is no end to the game: however big a number may be, we can always add 1 to produce a bigger number: the set of counting numbers is infinite. The concept of infinity has intrigued philosophers since antiquity, and it leads to many surprises and paradoxical results [TM110 or search for “thatsmaths” at irishtimes.com].
Continue reading ‘Enigmas of Infinity’
Published November 24, 2016
Tags: Analysis, History
FIg. 1: Brook Taylor (1685-1731). Image from NPG.
The English mathematician Brook Taylor (1685-1731) introduced the calculus of finite differences in his Methodus Incrementorum Directa et Inversa, published in 1715. This work contained the famous formula known today as Taylor’s formula. In 1772, Lagrange described it as “the main foundation of differential calculus” (Wikipedia: Brook Taylor). Taylor also wrote a treatise on linear perspective (see Fig. 1).
It is noteworthy that the series for , and were known to mathematicians in India about 400 years before Taylor’s time.
Continue reading ‘Taylor Expansions from India’
Published November 10, 2016
Published August 25, 2016
Tags: Analysis, Geometry
It is well-known that an ellipse is the locus of all points such that the sum of their distances from two fixed points, the foci, is constant. Thus, a gardener may map out an elliptical flower-bed by driving two stakes into the ground, looping a rope around them and pulling it taut with a pointed stick, tracing out a curve on the ground.
Continue reading ‘Slicing Doughnuts’
We consider the convergence of the random harmonic series
where is chosen randomly with probability of being either plus one or minus one. It follows from the Kolmogorov three-series theorem that the series is “almost surely” convergent.
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Published April 28, 2016
Tags: Analysis, modelling
The Gudermannian is named after Christoph Gudermann (1798–1852). The Gompertz function is named after Benjamin Gompertz (1779–1865). These are two amongst several sigmoid functions. Sigmoid functions find applications in many areas, including population dynamics, artificial neural networks, cartography, control systems and probability theory. We will look at several examples in this class of functions.
Continue reading ‘Sigmoid Functions: Gudermannian and Gompertz Curves’