Use of Miscellaneous`RealOnly` Package
- To: mathgroup at smc.vnet.net
- Subject: [mg25253] Use of Miscellaneous`RealOnly` Package
- From: "David Park" <djmp at earthlink.net>
- Date: Sun, 17 Sep 2000 04:47:32 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Dear MathGroup,
Is it possible to turn the Miscellaneous`RealOnly` package on and off?
Consider the following problem. I want to find the inverse of the following
function:
F[u_, v_] := {u^3, v - u}
eqns = Thread[F[u, v] == {x, y}]
{u^3 == x, -u + v == y}
sols = Solve[eqns, {u, v}][[1]]
{v -> x^(1/3) + y, u -> x^(1/3)}
If the above Solve is done with the RealOnly package active, it fails and
gives Nonreal for the answers. So I definitely don't want it active at this
point. Now I define the inverse:
FI[x_, y_] = ({u, v} /. sols)
{x^(1/3), x^(1/3) + y}
Now when I evaluate
FI[-10, -10] // N
{1.077217345015942 + 1.865795172362064*I, -8.922782654984058 +
1.865795172362064*I}
I obtain the complex root, so I need to load RealOnly package.
<< Miscellaneous`RealOnly`
FI[-10, -10] // N
{-2.15443, -12.1544}
So sometimes I want it, and sometimes I don't want it. But there seems no
way to get rid of it other than quitting the kernel.
Does anyone have any suggestions, or a smoother way to do this problem?
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/