Name: Andy E.
Why are the center points of a circle are represented by
(h, k), what do they stand for?
I would be surprised if they actually stand for anything. There is a very
important fact that must be realized when using variables. The letter used
does not have to stand for anything. For example, x is a common variable
used. The reason goes back to when writing was done with feathers dipped in
ink. "x" just happens to be one of the easiest letters to write with a
quill. It became a tradition to use an "x". The same applies to "y". You
can actually use any symbol for a variable, so long as you don't change the
symbol in the middle of your work. Using (h,k) is a tradition that many
mathematicians and scientists are familiar with. If everybody uses the same
traditions, we have less confusion when looking at each other's work. I
expect (h,k) is used because the letters look so different from x and y , as
well as different from a,b (often used to indicate the focus of an ellipse
or hyperbola). When everything was hand-written, this was a more important
point. Now, with word processors and electric typewriters, there is less
chance of misreading a variable.
Dr. Ken Mellendorf
Illinois Central college
I do not think there is any particular significance to the choice of (h,k)
nor do I think the practice is universally used in texts.
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Update: June 2012