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 ▼ Alberto Candel Unregistered Posts: 72 Threads: 16 Joined: Sep 2013 12-10-2013, 07:16 PM Hi, In CAS, for example, if I input ```taylor(LN(1+x),x,3) ``` the output is ```x -(1/2)*x^2+(1/3)*x^3+x^4*order_size(x) ``` as expected from the documentation. But ```taylor((x+x^2+2*x^3)/(1+2*x-x^2+6*x^3), x,3) ``` outputs ```x-x^2+5*x^3-17*x^4+x^5*order_size(x) ``` instead of ```x-x^2+5*x^3+x^4*order_size(x) ``` Why the extra term? ▼ parisse Unregistered Posts: 38 Threads: 0 Joined: Aug 2013 12-11-2013, 04:42 AM The third parameter is the order used for series expansion, not necessarily the final order. ▼ Alberto Candel Unregistered Posts: 72 Threads: 16 Joined: Sep 2013 12-11-2013, 08:20 AM Thank you. So if I want to obtain the Taylor polynomial of degree n of a function f(x), what is the correct command to use? (I want the result to be a polynomial of degree less than or equal to n, and I do not want the extra "order_size" term) ▼ parisse Unregistered Posts: 38 Threads: 0 Joined: Aug 2013 12-12-2013, 04:02 AM rem(convert(series(expression,x=limit_point,order),polynom),x^(order+1)) should do that: convert(.,polynom) will remove the order_size remainder term, and rem will remove all monomials of degree>=order+1. You have no warranty to get the full Taylor expansion however, since the remainder term has been erased... ▼ Alberto Candel Unregistered Posts: 72 Threads: 16 Joined: Sep 2013 12-13-2013, 09:41 PM Thanks. But it looks that such command is not available in the HP prime. The example in page 157 of the "Symbolic algebra and Mathematics with Xcas" ```convert(series(sin(x),x=0,6),polynom) ``` outputs ```"Error: Unmatch control word" ``` ▼ Alberto Candel Unregistered Posts: 72 Threads: 16 Joined: Sep 2013 12-13-2013, 09:45 PM But it looks like "truncate" is in Prime, and does more or less the same.

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