用Mathematica8解微分方程解不了,您知道是怎么回事吗?
今天用Mathematica8解方程解不了了,一直报错：
In[72]:=DSolve[y'[x]==E^x*y[x],y[x],x]
:6B63:5728:8BA1:7B97In[72]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
Out[72]=DSolve[E^xy==E^xy[x],y[x],x]
In[60]:=DSolve[y'[x]+2x*y[x]==x*Exp[-x^2/2],y[x],x]
:6B63:5728:8BA1:7B97In[60]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
Out[60]=DSolve[E^xy+2xy[x]==E^(-(x^2/2))x,y[x],x]
In[61]:=DSolve[y'[x]+y[x]==aSin[x],y[x],x]
:6B63:5728:8BA1:7B97In[61]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
Out[61]=DSolve[E^xy+y[x]==aSin[x],y[x],x]
In[62]:=DSolve[{y'[x]+y[x]==aSin[x],y[0]==0},y[x],x]
:6B63:5728:8BA1:7B97In[62]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
In[63]:=DSolve[{E^xy+y[x]==aSin[x],y[0]==0},y[x],x]
:6B63:5728:8BA1:7B97In[63]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
Out[63]=DSolve[{E^xy+y[x]==aSin[x],y[0]==0},y[x],x]
In[64]:=DSolve[y'[x]==x,y[x],x]
:6B63:5728:8BA1:7B97In[64]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
Out[64]=DSolve[E^xy==x,y[x],x]
In[69]:=DSolve[{E^xy+y[x]==aSin[x],y[0]==0},y,x]
:6B63:5728:8BA1:7B97In[69]:=DSolve::dvnoarg:Thefunctionyappearswithnoarguments.>>
Out[69]=DSolve[{E^xy+y[x]==aSin[x],y[0]==0},y,x]
仔细检查过输入了,没有问题,但是解这个又可以：
In[68]:=DSolve[{x'[s]==Cos[t[s]],y'[s]==Sin[t[s]],t'[s]==s,
x[0]==0,y[0]==0,t[0]==0},{x,y,t},s]
Out[68]={{t->Function[{s},s^2/2],
x->Function[{s},Sqrt[[Pi]]FresnelC[s/Sqrt[[Pi]]]],
y->Function[{s},Sqrt[[Pi]]FresnelS[s/Sqrt[[Pi]]]]}}
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