composition of functions - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: composition of functions (/thread-1865.html) composition of functions - Alberto Candel - 07-22-2014 01:23 AM Is there a command for the composition of two functions, f and g, in CAS? There is f@@g in xcas, but I do not seem to get it to work in the Prime. RE: composition of functions - Mark Hardman - 07-22-2014 02:17 AM (07-22-2014 01:23 AM)Alberto Candel Wrote:  Is there a command for the composition of two functions, f and g, in CAS? There is f@@g in xcas, but I do not seem to get it to work in the Prime. Try something along the lines of: f(x):=√(x²-1) g(x):=4*x The composition of the two functions is simply: f(g(x)) HTH RE: composition of functions - Alberto Candel - 07-22-2014 03:54 AM Thank you Mark. But I was looking for something like that on page 12 of this Xcas/giac tutorial RE: composition of functions - parisse - 07-22-2014 09:51 AM In Xcas, @ does function composition, not @@, @@ is for composition power. RE: composition of functions - Alberto Candel - 07-22-2014 03:44 PM (07-22-2014 09:51 AM)parisse Wrote:  In Xcas, @ does function composition, not @@, @@ is for composition power. Yes, thanks, I should have written f@g for the composition and f@@n for the composite of f with itself n times. The prime accepts f@g, but it seems to return a function like (x,y)->(f(x),g(y)) (if f and g are 1 variable functions). RE: composition of functions - parisse - 07-22-2014 04:07 PM Please give an example. RE: composition of functions - Alberto Candel - 07-22-2014 09:14 PM (07-22-2014 04:07 PM)parisse Wrote:  Please give an example. For instance f(x):=x^2 g(x):=x+1 f@g returns ((x)->x^2)@((x)->x+1) I do not know the meaning of @ RE: composition of functions - Mark Hardman - 07-22-2014 11:11 PM (07-22-2014 09:14 PM)Alberto Candel Wrote:   (07-22-2014 04:07 PM)parisse Wrote:  Please give an example. For instance f(x):=x^2 g(x):=x+1 f@g returns ((x)->x^2)@((x)->x+1) I do not know the meaning of @ The CAS is providing an intermediate solution to the composition. If you execute: simplify(f@g) You get the expected result: (_(x))->_(x)²+2*_(x)+1 RE: composition of functions - Alberto Candel - 07-23-2014 02:41 PM That works, thanks. But it would be better without the simplify part.  Actually, if you define k:=f@g, then k(x)=x^2+2*x+1, without the simplify.[/edit] RE: composition of functions - parisse - 07-23-2014 06:23 PM You can also type (f@g)(x). Note that f@g is a function, not an expression. RE: composition of functions - Alberto Candel - 07-23-2014 09:21 PM (07-23-2014 06:23 PM)parisse Wrote:  You can also type (f@g)(x). Note that f@g is a function, not an expression. Yes, thanks. I think my original mistake was to write f@g(x) instead of (f@g)(x).