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Thread: Associative Pet Peeve

  1. #1

    Associative Pet Peeve

    While preparing a loosely related presentation, I recently tripped over a webpage featuring a turorial for finding the circumference of a circle. π * diameter was the simple formula, correct? Negative.

    2πr

    I was genuinely offended and wondered if I was just being fussy. The next time I saw my mechanic, 2πr hit the shop whiteboard. After a brief pause to parse the equation, he almost punched me in the throat while barking, "never do that!"

    Then I saw the resident subject matter expert in early childhood development, with specific focus on education. It almost ended in me sleeping on the couch.

    The Associative Property reminds us that factors in a multiplicative equation can be grouped in any order without changing the product. Not should. Certainly not must.

    Pi times diameter is simple and easily internalized. As noted by my stalwart wrench, the diameter is usually known in practocal application to further bolster the forumula's memorization.

    2πr can give people pause. It is unclear and does nothing to add implied commentary to its function. But proper use of the Associative Property away from laziness and toward clarity could be applied for the better.

    2rπ

    π(2r)

    Utilize whitespace on the page to add a simple note about diameter. Anything but the unclear 2πr.

    This little peeve of modern laziness went forgotten for a week until I casually thumbed through a book on my desk. The Great International Math on Keys Book, Rev. B by Texas Industries Learning Center.

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    This book was written to accompany the first widely-adopted pocket calculator with algebraic order of operations. Nearly fifty years ago.

    *Insert profane indignance here*

  2. #2
    Site Supporter OlongJohnson's Avatar
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    Pi is about so much more than figuring out the circumference of a circle. If you got as far as trigonometry or know what a radian is, you probably see a lot of utility in working with r instead of D and are perfectly comfortable with 2pi()r. (Yes, I use a lot of Excel.)
    .
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    Not another dime.

  3. #3
    Site Supporter
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    2Pi*r

    Should make this a poll.
    "No free man shall ever be debarred the use of arms." - Thomas Jefferson, Virginia Constitution, Draft 1, 1776

  4. #4
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    Now I have an inexplicable urge to change my username to 2πr

  5. #5
    I'm an old timey engineer that used to use a slide rule and remember fondly getting my first scientific calculator my senior year in high school. 2 pi r (so old school I don't how to find Greek letters on my phone) is natural to me. Area is pi r squared, which is easier for most than calculating area as a function of diameter. My grandson is in 7th grade and I help him with math all the time and it seems simpler to me to keep it in terms of r. I've never given any thought to the order of terms at all.

  6. #6
    Things are taught the way they are for a reason.

    The reason is oftimes shit but there's still a reason.

  7. #7
    Site Supporter Oldherkpilot's Avatar
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    Dec 2019
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    Warren, Ohio
    I often find myself measuring the diameter of the round object in order to find the radius. I can see where just going with πD might be simpler but I learned 2πr and the brain cells I have left are best not toyed with!

  8. #8

  9. #9
    I can't count how many times I failed math class in high school.
    Is the boy you were proud of the man you are?

    Fimbo iliyo mkononi, ndio iuwayo nyoka!

  10. #10
    Site Supporter
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    Sep 2017
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    South Louisiana
    Cake r square.

    Pi r round.

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