#### 7.74 bug in int Maple V.51 to Maple 8 (24.9.01)

It sounds like int is having problem with integrating the following functions.

> z_modele_1:=x*cos(x)^3;
> z_modele_2:=sin(x)+x*cos(x)-sin(x/2);
> evalf(int(abs(z_modele_2-z_modele_1),x=0..5));
> evalf(Int(abs(z_modele_2-z_modele_1),x=0..5));
3
z_modele_1 := x cos(x)
z_modele_2 := sin(x) + x cos(x) - sin(1/2 x)
2.041317817
5.959032441

The correct answer is `5.95...`

.

These diﬀerences have been noticed both in Maple 6 `(build=16401)`

and Maple 7
`(build=96223)`

on Wintel.

This is a bug in int indeed.

Maple 6:

> K := int(abs(z_modele_2-z_modele_1),x=0..X):
> eval(K, X=0 );
-11/9

If you (only) need a numerical approximation of an integral, it is always better to use the
inert form Int.

Because:

`evalf(Int...)`

makes a numerical approximation of the integral;

`evalf(int...)`

ﬁrst integrates symbolically and calculates a numerical approximation of the
result.