Boxing Pythagoras

Philosophy from the mind of a fighter

Archive for the month “October, 2017”

On Wildberger’s “Inconvenient Truths”

Dr. Norman Wildberger of the University of New South Wales has a wonderful and prolific YouTube channel in which he discusses a great deal of very interesting mathematics. I have discussed Dr. Wildberger before, regarding a very similar subject, but I wanted to take a moment to discuss a video from his Math Foundations series entitled, “Inconvenient truths about sqrt(2).”

In the video, Dr. Wildberger claims that there are three different ways in which \sqrt{2} is commonly discussed: the Applied, the Algebraic, and the Analytical. He does a fairly good job of discussing the manner in which the ancient Greeks discovered that there exists no ratio of two whole numbers which can be equal to \sqrt{2}, which is a topic I have covered here, as well. He then explains what he means by each of the above three categories.

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Infinitesimal Calculus 2: The Changes in Change

The mathematics of change are quite interesting. In a naive sense, we can often describe a change by a simple collection of data points. For example, let’s think about a little boy rolling a ball across the floor. The boy pushes the ball, and four seconds later, the ball has come to be 2 meters away from him. Given these data points, we may attempt to connect them in some meaningful analytical manner– perhaps by saying that the ball rolled at a speed of half a meter per second. But even this is a somewhat naive bit of information, as it only really tells us something about the completed journey. Mathematicians are greedy, however; they want to be able to know about every point of the ball’s travel, at any arbitrary moment in time.

We can use a function for just such a purpose. A function is a specific mathematical tool which allows us to describe an entire set of data points all at once which we symbolize as f(x) (read “f of x“). We encode the data by means of a mathematical formula. For example, our exemplary rolling ball might well have been encoded by the function f(x)=\frac{1}{2}x, where the x represents the time, in seconds, that the ball has been rolling, and the value of the function, f(x) tells us the distance in meters which the ball has traveled in that time. In this particular function, the coefficient of x tells us the rate at which distance changes as time passes– that is, \frac{1}{2} a meter per second. When the boy first rolls it, the ball is traveling at \frac{1}{2} a meter per second; when it finishes it had been traveling at \frac{1}{2} a meter per second; and at any single point during the journey the ball is traveling at \frac{1}{2} a meter per second.

However, this is a very simple example. It describes a situation involving a constant velocity. Things become a bit more muddied when the rate at which a change occurs is, itself, changing.

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