But in general, you can't invert formulas (and even if you mathematically can, it doesn't mean that solve() can do it).
Aaron Meurer On Sat, Nov 2, 2013 at 8:14 AM, Saullo Castro <[email protected]> wrote: > To transform the variables "solve" and to do the back-substitution "subs"... > > > > 2013/11/2 F. B. <[email protected]> >> >> >> >> On Saturday, November 2, 2013 11:46:27 AM UTC+1, Saullo Castro wrote: >>> >>> I believe we can make a variable transform and then apply the derivative >>> using the expression converted to a variable, like: >>> >>> x = a**2 + c + d**3 >>> x.diff((a + c**2)) >>> >>> changing variables: >>> >>> v = a + c**2 >>> a = v - c**2 >>> c = (v-a)**0.5 >>> >>> the new x will be: >>> >>> x2 = (v-c**2)**2 + (v-a)**0.5 + d**3 >>> >>> and the derivative could be computed as: >>> >>> x2.diff(v) >>> >>> is that reasonable? >> >> >> Yes, it is. >> >> Are you going to use .subs( ) or solve( ) ? >> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "sympy" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/sympy/P8Q3G5bHe-U/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/sympy. >> For more options, visit https://groups.google.com/groups/opt_out. > > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
