# naginterfaces.library.specfun.integral_​cos¶

naginterfaces.library.specfun.integral_cos(x)[source]

integral_cos returns the value of the cosine integral

where denotes Euler’s constant.

For full information please refer to the NAG Library document for s13ac

https://www.nag.com/numeric/nl/nagdoc_28.5/flhtml/s/s13acf.html

Parameters
xfloat

The argument of the function.

Returns
cixfloat

The value of the cosine integral

Raises
NagValueError
(errno )

On entry, .

Constraint: .

The function has been called with an argument less than or equal to zero for which is not defined.

Notes

integral_cos calculates an approximate value for .

For it is based on the Chebyshev expansion

For ,

where and , .

For , to within the accuracy possible (see Accuracy).

References

NIST Digital Library of Mathematical Functions