CAS.diff command results diff command again

[josephec]

(06-11-2017 01:54 AM)toml_12953 Wrote:  

(06-10-2017 04:46 PM)josephec Wrote:  Thanks roadrunner,
I alredy tried EVAL(diff(fx,X))
The problem is if fx has funtion like 'SEC(X)+X^2'
diff returns diff(SEC(X),X)+2*X and EVAL will solve the diff issue but also will replace the X with its value.

I appreciate this and future suggestions.
Best regards!!
jose

I get the correct answer with eval and X keeps its old value. I set X:=2 then did EVAL(diff(fx,X)). That worked then when I typed in X and Enter
I got 2 back.

Tom L

Hi Tom
Thanks for trying and suggesting...

Quote:diff returns diff(SEC(X),X)+2*X and EVAL will solve the diff issue but also will replace the X with its value.

I mean that X´s value is replaced in the +2*X part ... but the solucion offered by Roadrunner works great using
CAS("fx:=SEC(x)+x^2")
CAS("subst(eval(diff(fx,x)),x='X')")
I appreciate Your time and suggestion.
Have an excellent week.
joseph