WILLIAM P. THURSTON ｗｗｗ（＾＾ （参考） https://arxiv.org/pdf/math/9404236.pdf APPEARED IN BULLETIN OF THE AMERICAN MATHEMATICAL SOCIETY Volume 30, Number 2, April 1994, Pages 161-177 ON PROOF AND PROGRESS IN MATHEMATICS WILLIAM P. THURSTON (抜粋) 2. How do people understand mathematics?
This is a very hard question. Understanding is an individual and internal matter that is hard to be fully aware of, hard to understand and often hard to communicate. We can only touch on it lightly here. People have very different ways of understanding particular pieces of mathematics. To illustrate this, it is best to take an example that practicing mathematicians understand in multiple ways, but that we see our students struggling with. The derivative of a function fits well. The derivative can be thought of as: (1) Infinitesimal: the ratio of the infinitesimal change in the value of a function to the infinitesimal change in a function. (2) Symbolic: the derivative of x^n is nx^(n-1), the derivative of sin(x) is cos(x), the derivative of f ・ g is f′ ・ g * g′, etc. (3) Logical: f′(x) = d if and only if for every ε there is a δ such that when 0 < |Δx| < δ, |{(f(x + Δx) - f(x))/Δx}- d |< δ. (4) Geometric: the derivative is the slope of a line tangent to the graph of the function, if the graph has a tangent. (5) Rate: the instantaneous speed of f(t), when t is time. (6) Approximation: The derivative of a function is the best linear approximation to the function near a point.
(7) Microscopic: The derivative of a function is the limit of what you get by looking at it under a microscope of higher and higher power.
https://rio2016.5ch.net/test/read.cgi/math/1592578498/713-714 This is a list of different ways of thinking about or conceiving of the derivative, rather than a list of different logical definitions. Unless great efforts are made to maintain the tone and flavor of the original human insights, the differences start to evaporate as soon as the mental concepts are translated into precise, formal and explicit definitions. I can remember absorbing each of these concepts as something new and interesting, and spending a good deal of mental time and effort digesting and practicing with each, reconciling it with the others. I also remember coming back to revisit these different concepts later with added meaning and understanding. (引用終り)
