CIN

This function evaluates a function closely related to the cosine integral.

Function Return Value

CIN — Function value. (Output)

Required Arguments

X — Argument for which the function value is desired. (Input)

FORTRAN 90 Interface

Generic: CIN (X)

Specific: The specific interface names are S_CIN and D_CIN.

FORTRAN 77 Interface

Single: CIN (X)

Double: The double precision function name is DCIN.

Description

The alternate definition of the cosine integral, Cin(x), is

 

For

 

where s = AMACH(1) is the smallest representable positive number, the result underflows. For

 

the answer is less accurate than half precision, while for ∣x∣ > 1 /ɛ, the answer has no precision. Here, ɛ = AMACH(4) is the machine precision.

Comments

Informational Error

 

Type	Code	Description
2	1	The function underflows because X is too small.

Example

In this example, Cin(2π) is computed and printed.

 

USE CIN_INT

USE UMACH_INT

USE CONST_INT

 

IMPLICIT NONE

! Declare variables

!

INTEGER NOUT

REAL VALUE, X

! Compute

X = CONST('pi')

X = 2.0* X

VALUE = CIN(X)

! Print the results

CALL UMACH (2, NOUT)

WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' CIN(', F6.3, ') = ', F6.3)

END

Output

 

CIN( 6.283) = 2.438