XLPack 7.0
XLPack Numerical Library (C API) Reference Manual
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◆ chebu()

double chebu ( unsigned int  n,
double  x 
)

Chebyshev polynomial of second kind Un(x)

Purpose
chebu computes the Chebyshev polynomial of the second kind Un(x).
Un-1(x) = sin(nt)/sin(t), where x = cos(t)
This polynomial follows the recurrence formula:
Un+1(x) = 2xUn(x) - Un-1(x), where U0(x) = 1, U1(x) = 2x (n > 0)
Returns
Chebyshev polynomial of second kind Un(x).
Parameters
[in]nArgument n.
[in]xArgument x.
Error handling
  • Range error (ERANGE) may occur.
Note
  • If x < -1 or x > 1, this routine is much slower and recommended not to be used.
Reference
boost/math/special_functions