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Re: DSolve question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88800] Re: DSolve question
  • From: igwood <igwood at yahoo.co.jp>
  • Date: Fri, 16 May 2008 05:37:05 -0400 (EDT)

Below is the code that works. Clearly Mathematica recognizes output in curly braces {  } differently than that without. 

In[1]:= Duty = .6; SWfreq = 1*10^6; Vin = 3.2; Vout = 1.8; L = 
 4.7*10^-7; R = 0.008;

In[2]:= Dt1 = 
 Duty (1/SWfreq); Dt2 = (1 - Duty) (1/SWfreq); VL2 = - Vout; VL1 = 
 Vin - Vout; T = 1/SWfreq;

In[3]:= it1 = 
 Simplify[DSolve[{L i1'[t] + R i1[t] - VL1 == 0, i1[0] == a1}, i1[t], 
   t]]

Out[3]= {{i1[t] -> 175.+ (-175. + 1. a1) E^(-17021.3 t)}}

In[4]:= it2 = 
 Simplify[DSolve[{L i2'[t] + R i2[t] - VL2 == 0, i2[0] == a2}, i2[t], 
   t]]

Out[4]= {{i2[t] -> -225. + (225.+ 1. a2) E^(-17021.3 t)}}

In[5]:= i1[t_] = 
 175.00000000000003`+ (-175.00000000000003` + 
     1.` a1) E^(-17021.276595744683` t)

Out[5]= 175.+ (-175. + 1. a1) E^(-17021.3 t)

In[6]:= i2[t_] = -225.` + (225.`+ 1.` a2) E^(-17021.276595744683` t)

Out[6]= -225. + (225.+ 1. a2) E^(-17021.3 t)

In[7]:= FindRoot[{i1[0] == i2[T], 
  i1[Dt1] == i2[Dt1]},
 {a1, 0}, {a2, 0}]

Out[7]= {a1 -> 14.1825, a2 -> 18.2886}


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