Pi Day Pointer

Just a quick Pi Day pointer for you geometry teachers: be sure to stress to students that Pi is a constant rather than a variable. The misconception that it’s a variable comes in part from the fact that we often express circumference and area in terms of Pi. I especially notice confusion when students work with the formula, Circumference = 2πr (something about multiplying the two outer factors, r and 2, and leaving π alone that gives students the impression that π is a variable).

Happy Pi Day!


One Response to Pi Day Pointer

  1. Cynthia Paul says:

    It is important to emphasize that pi is the ratio between the circumference and the diameter of a circle, any circle. I have always found it fascinating that you can take any circle’s circumference, divide by the same circle’s diameter, and get one number, which is pi.

    I realize that all of you know this already but I love this truth and always share it with my students. It is an instructive exercise for students to measure the circumference and diameter of a variety of circles and find this out for themselves. (Most can use the practice measuring, as well!)

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