XPost: sci.math   
   From: ivgroups@onlinehome.de   
      
   "Dale"  wrote in news:lvkujt$vu9$2@speranza.aioe.org...   
   >>> df(x)/dx at x = f_(x)   
   >> It is the same as df(f_(x))/df_(x).   
   > not sure what you mean by f_(x) ?   is that  f superscript -1 meaning   
   > inverse function?   
   Yes. Uppermost I wrote: "the compositional inverse f_ = f_(x) of a given   
   function f = f(x)".   
      
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