[Scilab-users] Sine integral

[Federico Miyara]

Dear All,

Is there a primitive implementing the sine(x)/x indefinite integral 
(called sine integral, Si)?

I couldn't find it either among the special functions or trigonometric 
functions collections. It is an important function in signal processing 
(for instance a non-aliased rectangular pulse requires Si).

I know it would be possible to find the value for given x using 
integrate or intg, but I'm sure it would be much more efficient to use 
an approximation such as a Taylor series combined perhaps with an 
asymptotic approximation, than to massively compute a definite integral 
for each single value.

Regards,

Federico Miyara
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