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Surprising DSolve problem

• To: mathgroup at smc.vnet.net
• Subject: [mg123944] Surprising DSolve problem
• From: Sam Takoy <sam.takoy at yahoo.com>
• Date: Mon, 2 Jan 2012 02:42:06 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hi,

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?

Thanks,

Sam

• Follow-Ups:
  • Re: Surprising DSolve problem
    • From: DrMajorBob <btreat1@austin.rr.com>
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    • From: "Scot T. Martin" <smartin@seas.harvard.edu>
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