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Surprising DSolve problem

  • To: mathgroup at
  • Subject: [mg123944] Surprising DSolve problem
  • From: Sam Takoy <sam.takoy at>
  • Date: Mon, 2 Jan 2012 02:42:06 -0500 (EST)
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I find that my Mathematica (8.0.1)

can do

DSolve[ y''[x] + (2 y[x])/(Cosh[x]^2) == 0, y, x]

but can't do

DSolve[ y''[x] + (2 y[x])/(a^2 Cosh[x/a]^2) == 0, y, x] (*Additional
constant "a")

If I am not mistaken, the equations are equivalent by a trivial change
of variables.

What's going on here?



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