## 25 Reputation

19 years, 274 days

## intsolve error for Abel integral equatio...

Maple

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.

## Problematic differentiation of a sum ...

Maple

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]);
N
-----
\
)
/    cos(x[i])
-----
i = 1

which is wrong of course.

## Bug is sum when start index larger than ...

Maple

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
sum(1,j=i..1);
end do;
2
1
0
-1
-2

## plot3d error message...

Maple 16

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);
/Pi
...

## Trouble differentiating Int with option...

Maple

Hi,

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 ?

Thanks,

Dan

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