Solve[] handles the same system differently
- To: mathgroup at smc.vnet.net
- Subject: [mg40841] Solve[] handles the same system differently
- From: Joe Gwinn <joegwinn at attbi.com>
- Date: Mon, 21 Apr 2003 06:59:15 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
I am running Mathematica 4.0.1.0 under MacOS 9.1, and have encountered a
little mystery:
The following works OK:
In[15]:=
Solve[{Rx == 3300, VinX1 == 0,
IdsX1 == 0.001(1 - (VinX1 - Rx*IdsX1)/(-1.5))^2}, {IdsX1}]
Yielding:
Out[15]=
{{IdsX1 -> 0.000234453}, {IdsX1 -> 0.00088125}}
When I rearrange the equation system a bit, it fails to find a solution:
In[16]:=
Solve[{Rx == 3300, VinX1 == 0, VgsX1 == Rx*IdsX1,
IdsX1 == 0.001(1 - (VinX1 - VgsX1)/(-1.5))^2}, {IdsX1}]
Out[16]=
{}
What's going on? Why does a little algebra (the creation of the
variable VgsX1) cause a problem? In[16] was generated by copying In[15]
and doing some editing. No error messages were generated by either.
Thanks,
Joe Gwinn