Circles for Dummy Geometry Students, Again

finding the center of a circle

We have a staffer who regularly checks our older DotD nominations for broken links or links that lead to "deprecated" pages. It seems that from time to time, the people at Leaf Group have a member of their stable of "experts" clean up older posts that someone (not us) has found wanting. Sadly, the reworked content can be no better than the original. Here's what happened when we checked Rachel Pancare's post on "How to Determine the Diameter of a Circle": we found a rework by Claire Gillespie that wasn't much better...

Gillespie introduced her topic by explaining what a circle is. In reality, she just reworded the definition of a circle, and she didn't do a very good job:

"A circle is the set of all points in a plane that are a fixed distance from a fixed point."

What she really means is "equidistant from a fixed point," but that would have tripped the plagiarism detector. From this point onward, Claire manages to explain two different ways to calculate the diameter of a circle:

• "Multiply Radius by Two"
• "Divide Circumference by Pi Constant"¹

Yes, Gillespie does indeed think there's such a thing as a "Pi Constant," which she explains thus:

"Pi, a never-ending string of numbers, is the ratio of the circumference of a circle to its diameter."

Unfortunately, that's not quite correct. One divided by three results in a "never-ending string of numbers" but π differs in that it's non-repeating (an important distinction, in our humble opinion). Besides the fact that she refers to the "pi constant" several times, Claire also blew her assignment on a very important point: How do you determine the radius (for measurement) if you don't know the center? Our sister blog, The Fixit Zone, can answer that for you!

Like Pancare before her, Claire ignored the geometric quandary of determining the center of a circle. What's unfortunate is that the first time this "title" was published, an eHow.com contributor named Kim Hoyum answered that question. Apparently, the SEO gurus at eHow decided her answer was too long. So they reduced its usefulness to make it shorter. Duh.

We can't give them the Dumbass of the Day award, though, so we'll give it to Gillespie instead.

¹ Some time after we called Gillespie on her "Pi Constant" bushwa, the site owners cleanup up that crap and changed the wording to "pi." If you'd like to see the original, check out the Wayback machine at archive.org, looking at the 2019 version of   sciencing.com/determine-diameter-circle-5743525.html

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