Do you know what a locus is?

[Romeo]

A locus is a set of points that satisfy a certain condition. Or so my maths teacher taught me many years ago. To this day I still don't have a clue what she was on about. Can anyone explain it more simply?

[fo3nix]

Imagine you have a point on a piece of paper, and want to draw a curve that is at the same distance from the point everywhere on the curve. You're being asked to draw a locus -- the curve is a set of points and it's satisfying a condition (that they're all the same distance from the point).

In the above example, the locus would be a circle.

Image you have a line now on some paper, and are set the same problem -- how to draw something that's the same distance from the line all over? The solution is to draw a horizontal line above and below the line, parallel to it, and then draw a semicircle on either end of the line, to join up the lines you've just drawn.

(Sorry, it may sound a bit confusing when you can't see a picture.)

[Kidd72]

Excellently explained fo3nix iv never heard of locus before or just totally forgot about it, fully understand now. Have a gold star and a tick.

[Romeo]

Thanks, fo3nix. I think I understand now. Basically, it's an equidistant outline around a point or line. OK.

[fo3nix]

Yes, it can be that. That's the certain condition that you often have to satisfy, but as far as I can gather you could set another specific condition to where the locus should be or what it should do, and it would still be a locus.

I was taught them at GCSE, but haven't used them since (at least, not by specifically calling them loci).