Re: DSOLVE in 5.01 ??

*To*: mathgroup at smc.vnet.net*Subject*: [mg47623] Re: DSOLVE in 5.01 ??*From*: "Peter Pein" <petsie at arcor.de>*Date*: Sun, 18 Apr 2004 04:15:26 -0400 (EDT)*References*: <c5j82s$r3h$1@smc.vnet.net> <c5oaui$1fl$1@smc.vnet.net> <c5qj6n$fvp$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

"turbo cyx" <turbocyx at gmx.net> schrieb im Newsbeitrag news:c5qj6n$fvp$1 at smc.vnet.net... > Why should I bother with this?? I am not willing to use workarounds > for Wolfram bugs (I am coauthor of a widely used courseware in > austria. Now I have to write this workaround for all the Lessons wich > use DSolve and boundary conditions, in a few month when 6.0 finally is > available I can undo this again ....) > Mathematica 4.2 (and all previous version) has been able to solve this system, > so I think 5.01 should be also (BTW: 6.0 Alpha can solve this system > again) > Wolfram where is a bugfix > Cyx > Mathematica 4.0 must have been published after vers. 4.2: In[1]:= $Version dgl1 = m*g - c*v[t]^2 == m*Derivative[1][v][t]; dgl2 = Derivative[1][s][t] == -v[t]; DSolve[{dgl1, dgl2, s[0] == h0, v[0] == 0}, {s[t], v[t]}, t] Out[1]= 4.0 for Microsoft Windows (July 16, 1999) From In[1]:= Solve::incnst: Inconsistent or redundant transcendental equation. After Sqrt[g] Sqrt[m] C[2] 2 reduction, the bad equation is 1 - Cosh[--------------------] Sqrt[c] == 0. From In[1]:= Solve::incnst: Inconsistent or redundant transcendental equation. After Sqrt[g] Sqrt[m] C[2] 2 reduction, the bad equation is 1 - Cosh[--------------------] Sqrt[c] == 0. From In[1]:= Solve::tdep: The equations appear to involve the variables to be solved for in an essentially non-algebraic way. From In[1]:= DSolve::dsing: Unable to fit initial/boundary conditions {s[0] == h0, v[0] == 0} . Out[4]= {} In[5]:= DSolve[{dgl1,v[0]==0},v[t],t] Out[5]= Sqrt[c] Sqrt[g] t Sqrt[g] Sqrt[m] Tanh[-----------------] Sqrt[m] {{v[t] -> ---------------------------------------}} Sqrt[c] In[6]:= Integrate[-v[t]/.%[[1]],{t,0,z}]+h0 Out[6]= Sqrt[c] Sqrt[g] z m Log[Cosh[-----------------]] Sqrt[m] h0 - ------------------------------ c please check your statements _before_ posting (b.t.w. are you known as steve_H in sci.math.symbolic?). Thanks -- Peter Pein, Berlin to write to me, start the subject with [