Re: Surprising DSolve problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg123979] Re: Surprising DSolve problem*From*: "Dave Snead" <dsnead6 at charter.net>*Date*: Tue, 3 Jan 2012 05:29:47 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201201020742.CAA09063@smc.vnet.net>

Sam, Mathematica is deficient in this area. (Hopefully they'll improve this someday) Use it to solve y''[x] + (2 y[x])/(Cosh[x]^2) == 0 for y and then substitute x->x/a for a solution to y''[x] + (2 y[x])/(a^2 Cosh[x/a]^2) == 0 Cheers, Dave Snead -----Original Message----- From: Sam Takoy Sent: Sunday, January 01, 2012 11:42 PM To: mathgroup at smc.vnet.net Subject: [mg123979] Surprising DSolve problem 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

**References**:**Surprising DSolve problem***From:*Sam Takoy <sam.takoy@yahoo.com>