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Re: stupid question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34103] Re: [mg34081] stupid question
  • From: BobHanlon at aol.com
  • Date: Sat, 4 May 2002 04:28:21 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 5/2/02 4:36:58 AM, heimantj at celera.com writes:

>I am a mathematica newbie.  I have a first order equation that
>describes the amount of a compound at time t, it is a periodic system
>and the compound is either present or not (a step function):
>
>dA(t)/dt=S(t)-ln(2)/halflife*A(t)
>
>S(t) = S  if T1<t<t2
>S(t) = 0 otherwise
>
>Does anybody have an idea how I would solve this using mathematica to
>obtain the formal solution.  I would really appreciate any
>suggestions!!  Thankyou!!
>

eqn =
 
    (A'[t]== S*(UnitStep[t-t1]-UnitStep[t-t2])-Log[2]/halflife*A[t]);

soln = DSolve[eqn, A[t], t]//
 
     Flatten//FullSimplify

with a boundary condition

soln = DSolve[{eqn,A[0]==0},
 
        A[t], t]//Flatten//FullSimplify


Bob Hanlon
Chantilly, VA  USA


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