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Question about Solve (on mma2.2)
*To*: mathgroup at yoda.physics.unc.edu
*Subject*: Question about Solve (on mma2.2)
*From*: haras at vermeer.c.u-tokyo.ac.jp
*Date*: Sat, 18 Dec 93 21:51:06 +0900
Hello,
Please tell me how to get roots(intersection?) of simultaneous
nonlinear equations when variables are REAL.
Example1: [ x,y,z are real variables.]
---
f1 = x^2 + y^2 + z^2 -1;
f2 = (x-2)^2 + y^2 + z^2 -1;
Solve[ f1==0 && f2==0, {x,y,z}]
Out[3]= {{y -> -I z, x -> 1}, {y -> I z, x -> 1}}
---
{x->1,y->0,z->0} is a result that I want.
Example2: [ x,y,z are real variables.]
---
f1 = x^2 + y^2 + z^2 -1;
f2 = (x-5)^2 + y^2 + z^2 -1;
Solve[ f1==0 && f2==0, {x,y,z}]
2 2
Out[3]= {{y -> -Sqrt[-3 - z ], x -> 2}, {y -> Sqrt[-3 - z ], x -> 2}}
---
In this case , {f1==0} does not intersect {f2==0} and
Sqrt[-3-z^2] is not real when z is real.
My ideal result is a null list.
Is it necessary to use a Package for nonlinear programming ?
Thanks in advance.
HARASHIMA Seigo ( haras at vermeer.c.u-tokyo.ac.jp )
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