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Name:  Andy E.
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Question:
Why are the center points of a circle are represented by (h, k), what do they stand for?



Replies:
Andy,

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.

Vince Calder



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