Talk:Kronecker delta

Note to self: In Mathematica, test KroneckerDelta[1, 1.0000000000001] and KroneckerDelta[Sin[2017 * 2^(1/5)], -1] Alonso del Arte 02:48, 18 July 2010 (UTC)

Just tested both of those in Wolfram Mathematica 7.0, both return 0. However, KroneckerDelta[1, 1.0000000000000000000000000001] returns 1. Alonso del Arte 20:45, 19 July 2010 (UTC)

What is the default precision (how many significant digits?) of Mathematica 7.0?

Well, $MachinePrecision is 15.9546 (just like the manual says), but default display precision is just five digits (e.g., N[Pi] gives 3.14159). One can ask for more precision and Mathematica can deliver, up to a point.

With KroneckerDelta[1.0000000000001, 1], Mathematica still returns zero. But insert just another zero to push the decimal 1 to lesser significance and it returns 1. I was alerted to this after reading about it here: http://reference.wolfram.com/mathematica/ref/KroneckerDelta.html (under "Possible Issues"). (That documentation, by the way, is also available offline (i. e., not from the Web) from within the Mathematica program itself). Alonso del Arte 22:24, 19 July 2010 (UTC)