3.5.2.5.21 Cos_integral

Definition:

Ci=cos\_integral(x) evaluates

C_i\left( x\right) =y+\ln x+\int_0^x\frac{\cos u-1}udu
C_i\left( x\right) =y+\ln x+\int_0^x\frac{\cos u-1}udu

where \gamma denotes Euler's constant. The approximation is based on several Chebyshev expansions.

For more information please review the s13acc function in the NAG document.

Parameters:

x (input, double)
The argument x of the function.
Constraint: x>0.0
Ci (output, double)
The approximation of the formula C_i\left( x\right) =y+\ln x+\int_0^x\frac{\cos u-1}udu,x>0