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These are questions asked by danielpf

The Abel integral equation of the form

g(x) =  Int( f(y) / (x-y)^alpha, y = 0 .. x ) assuming alpha>0, alpha<1;

is linear and has a well known explicit solution for f(x).  

It is a particular form of Volterra equation of the first kind. 

It occurs in many problems of physics with alpha = 1/2.

However intsolve gives an error message:

> eq := g(x) =  Int(f(y)/(x-y)^alpha, y = 0 .. x) assuming alpha>0, alpha<1

> intsolve(eq, f(x));
Error, (in intsolve) numeric exception: division by zero

Replacing (x-y)^alpha by sqrt(x-y) gives the same error message.

Suppose a sum of sines, each depending on a distinct variable x[i]:

>  S := sum(sin(x[i]),i=1..N);

Differentiating wrt to x[i]

> diff(S,x[i]);

should yield cos([x[i]) if i belongs to the interval 1..N, and zero otherwise, but Maple gives

> diff(S,x[i]);
                         /    cos(x[i])
                        i = 1          

which is wrong of course.


In a sum I would expect 0 when the minimum index is larger than the maximum index.

Yet Maple 2017.3 does this only for special cases:

> for i from 0 to 4 do
  end do;




Hi experts!

Suppose we want to plot a function depending on integral evaluation, like

> S := Int(sin(sin(x+u)+sin(y-u)),u=0..Pi);


I meet a problem when I want to find the derivative of an integral with parameters when th eintegral has an option for numerical evaluatio.  For example

>  S := Int(sin(a*x)/x,x=0..infinity,method=_DEFAULT);

> diff(S,a);

Error, (in diff/Int) invalid Int(...) format

What is the correct syntax ?





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