Mantaining the same form

*To*: mathgroup at smc.vnet.net*Subject*: [mg124039] Mantaining the same form*From*: Miguel Gil <misvrne at gmail.com>*Date*: Sat, 7 Jan 2012 05:15:59 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Reply-to*: comp.soft-sys.math.mathematica at googlegroups.com

At a function in which one parameter is an expression "expr", Mathematica 8.0 evaluates or simplifies the value of "expr" when it is introduced. How is that Mathematica keep the same form of the "expr" introduced?. Example: In []: MyFunction [expr_]: = expr; MyFunction [(Sin [2x], Tan [y]) / (x * Sec [y]^2)] Out []: (Cos [y]^2 (Sin [2x], Tan [y]) / x I want to get the same expression (Sin [2x], Tan [y]) / (x * Sec [y]^2) Clearly, the input expression and modified expression are equivalent, but are not equal. For example, if we were to apply the rule of L'Hopital or the theorem Schwarz the results would be erroneous. Thanks