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Hello people in mapleprimes,

I want to ask you about how to make a function of function which makes a logarithmic derivative of a function.

For example, x^3 is mapped as h(x^3)=3h(x), h(x+y)=(x/(x+y))*h(x)+(y/(x+y))*h(y),


I hope someone give me a hing to create h.


Best wishes.






I wish to define a function which is the derivative of another function.

> f:=(x)->x^2:

> g:=(x)->diff(f(x),x):

> g(x);

2 x

> f(2);


> g(2);
Error, (in g) invalid input: diff received 2, which is not valid for its 2nd argument


I cannot find a way in which I can define the function g, using the functional operator, so that I can actually evaluate g(x).


How can I do this?



     I now have a problem.

     I want to calculate first derivative of a function and make it a function with respect to a variable.

     For example,




     I expect derivative is a function, (i.e.  derivative(x)=2x) , So if I put 'derivative(2)',I should get 4 as results. However I get "Error, (in H_Mag_Derivative_2) invalid input: diff received 2, which is not valid for its 2nd argument".

     Could someone give me a hand? Very much appreciated.

Hi evrey ones in pdsolve we have these commande to use U(x,t) 

> U:= subs(pds:-value(output=listprocedure), u(x,t));

  id like to get du(x,t)/dt

i tried these  

U:= subs(pds:-value(output=listprocedure), du(x,t)/dt);  but is not work 

thank you 


Dear all

I need a help to compute the integral from -1 to 1 of product of derivative of legendre polynomial

> restart;
> with(orthopoly);

P(n, x); # Designe the legendre polynomial of degree n
I would like to compute

int(diff(P(n,x),x)*diff(P(m,x),x),x=-1..1) ;


In this previous formula when I put n=2 and m=3 I can get the result but in general  case i cannot,

Many thanks



How I can write a procedure with Maple 18 that it receives function f(x) and x=a as inputs, 
then compute f'(a) and shows in output these 2 cases:

1) value f'(a)
2) curves f(x) ,y=f'(a)*(x-a)+f(a) and also the point (a,f'(a)) in a system ?

I am fairly new to Maple and cannot figure this out.

I'm having some trouble in computing formally the derivatives of
some composite functions

h:= x -> f(g(x)),

imposing conditions on the unknown functions f and g.

For example, I cannot find a way to impose g'(0)=0,
such that the computation of


simply gives 0.


Thank you in advance!

Sorry for disturbing you again. I am haunted by a problem about Taylor expansion in Maple.

For example, when the angle alpha is small, thus we could use taylor(sin(x),x=0,1) to get a approximated function of sin(x) with different order of precision.

But, if the sin(x) meets diff(x(t),t), (x is a time-dependant variable), could we also apply the Tayolr expansion in Maple to obtain a approximation?

For example, the function: sin(x(t))*diff(x(t),t), x(t) is given with a small value, but diff(x(t),t) could not be neglected, because even x(t) is with a small value , diff(x(t),t) could be great. We could conduct the Talyor expansion with hands, and sin(x(t))*diff(x(t),t) becomes x(t)*diff(x(t),t). But I wonder if we could use Maple to realize this procedure. And if the Maple could make it, I would like to know if the Maple could handle the multi-variable Taylor expansion accompanied with the time derivative. For example, the x(t) and y(t) are considered as small value variables, could we simplified the following function sin(x(t))*cos(y(t))*diff(x(t),t)*diff(y(t),t).

Thank you very much in advance for taking a look. 



I am new to Maple and discovering its features. I was wondering whether it is possible to define a function abstractly, say:


and differentiate it, to obtain f'(1/x) (-1/x^2)? Is this possible?



I wonder if there is any way to sort expressions like




how to sort  to


I have the following expression.


What I want to do is take the derivative of this expression with respect to,


Where L is somewhere between 1 and n. 

Using the diff operator, I would like to get something like,


But I don't.  Instead, I get zero.  I want to leave n undefined so that the summation isn't automatically expanded out to alot of terms, thereby making it much more difficult to read.  This is especially true as my formulas become more complicated.




See attached file and code

0. This is the differential equation I'm trying to do:


1. After you look at the above imgur link, could you help me with this error 

Error, (in Units:-Standard:-+) the units ``Ω`` and `1/F` have incompatible dimensions


2. Why does my solve ODE fail? 


See my code:

hi. i am tottaly new to the maple and i have a problem.

consider function f with variables x & y which are not independent. x & y are functions of t and the relation is unknown.

for example i wanna to the below job:

define f as f=x^2+y^2

differentiate it with respect to t : diff(f,t) which should give me 2(dx/dt)x+2(dy/dt)y

i've googled it alot and i couldn't find anything usefull.

(the problem is how to set x as a function of t with unknown relation and use it in another function and then differentiate it with respect to t)

thanks alot :)


I have functions like

g := (y, t)->sin(y(t))

diff(g(y, t), t) # ok

How to determine the derivative below with maple :

diff(g(y, t), y(t))


I have an ODE with L(x,y), which includes partial derivatives of L(x,y) and coefficients y,_y1 and _y1^2. I want to split this equation into seperate equations of these coefficients. So I can solve for the unknown variable L(x,y).



Could someone help me? 


I am currently trying to use the coeffs command but not really getting anywhere.


Thank you.

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