In the summer of 1994, I was teaching Calculus for the first time. When we got to the applications of derivatives, we talked about critical numbers being the potential relative extrema and identified them as points where f'(x)=0 or f'(x) is undefined. In the very next section, we came across possible inflection points that consisted of points where f"(x)=0 or f"(x) is undefined. I was surprised to see that there was no name for these points. So, I began calling them Hergert Numbers. In the years that followed, I taught the course many, many times. Each semester I would refer to these points as the Hergert Numbers, yet the term just didn't seem to be catching on - until now.
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If you would like your own Hergert Numbers t-shirt, email me at Rodger (at) hergertnumbers (dot) org and I'll hook you up. Once you have your shirt, get your picture taken in an interesting place or with an interesting person and I'll add you to the page.