By Paul J. Nahin

Today complicated numbers have such frequent functional use--from electric engineering to aeronautics--that few humans may count on the tale at the back of their derivation to be choked with event and enigma. In *An Imaginary Tale*, Paul Nahin tells the 2000-year-old heritage of 1 of mathematics' such a lot elusive numbers, the sq. root of minus one, often referred to as *i*. He recreates the baffling mathematical difficulties that conjured it up, and the colourful characters who attempted to unravel them.

In 1878, whilst brothers stole a mathematical papyrus from the traditional Egyptian burial web site within the Valley of Kings, they led students to the earliest identified incidence of the sq. root of a damaging quantity. The papyrus provided a selected numerical instance of the way to calculate the quantity of a truncated sq. pyramid, which implied the necessity for *i*. within the first century, the mathematician-engineer Heron of Alexandria encountered *I *in a separate venture, yet fudged the mathematics; medieval mathematicians stumbled upon the idea that whereas grappling with the which means of unfavorable numbers, yet pushed aside their sq. roots as nonsense. by the point of Descartes, a theoretical use for those elusive sq. roots--now known as "imaginary numbers"--was suspected, yet efforts to resolve them resulted in excessive, sour debates. The infamous *i* eventually received popularity and was once positioned to exploit in complicated research and theoretical physics in Napoleonic times.

Addressing readers with either a basic and scholarly curiosity in arithmetic, Nahin weaves into this narrative interesting ancient evidence and mathematical discussions, together with the appliance of complicated numbers and services to big difficulties, comparable to Kepler's legislation of planetary movement and ac electric circuits. This ebook may be learn as a fascinating heritage, virtually a biography, of 1 of the main evasive and pervasive "numbers" in all of mathematics.

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**Extra resources for An Imaginary Tale: The Story of ?-1**

**Example text**

Much of the mystery, the near-mystical aura, of ͙Ϫ1 was cleared away with Bombelli’s analyses. There did remain one last intellectual hurdle to leap, however, that of determining the physical meaning of ͙Ϫ1 (and that will be the topic of the next two chapters), but Bombelli’s work had unlocked what had seemed to be an unpassable barrier. 7 A Curious Rediscovery There is one last curious episode concerning the Cardan formula that I want to tell you about. About one hundred years after Bombelli explained how the Cardan formula works in all cases, including the irreducible case where all roots are real, the young Gottfried Leibniz (1646–1716) somehow became convinced the issue was still open.

It would be a thousand years more before a mathematician would even bother to take notice of such a thing—and then simply to dismiss it as obvious nonsense—and yet five hundred years more before the square root of a negative number would be taken seriously (but still be considered a mystery). While Heron almost surely had to be aware of the appearance of the square root of a negative number in the frustum problem, his fellow Alexandrian two centuries later, Diophantus, seems to have completely missed a similar event when he chanced upon it.

11 CHAPTER ONE too, will use j rather than i for ͙Ϫ1 when I show you a nice little electrical puzzle from the nineteenth century. , (a ϩ ib) (c ϩ id) ϭ ac ϩ iad ϩ ibc ϩ i2bd ϭ ac Ϫ bd ϩ i(ad ϩ bc). But you do have to be careful. For example, if a and b can both only be positive, then ͙ab ϭ ͙a ͙b. , ͙(Ϫ4)(Ϫ9) ϭ ͙36 ϭ 6 ͙Ϫ4 ͙Ϫ9 ϭ (2i)(3i) ϭ 6i2 ϭ Ϫ6. Euler was confused on this very point in his 1770 Algebra. One final, very important comment on the reals versus the complex. Complex numbers fail to have the ordering property of the reals.