diff options
Diffstat (limited to 'boost/math/special_functions/detail/bessel_y0.hpp')
| -rw-r--r-- | boost/math/special_functions/detail/bessel_y0.hpp | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/boost/math/special_functions/detail/bessel_y0.hpp b/boost/math/special_functions/detail/bessel_y0.hpp index 289bda5f18..533ab7c8a0 100644 --- a/boost/math/special_functions/detail/bessel_y0.hpp +++ b/boost/math/special_functions/detail/bessel_y0.hpp @@ -197,11 +197,22 @@ T bessel_y0(T x, const Policy& pol) { T y = 8 / x; T y2 = y * y; - T z = x - 0.25f * pi<T>(); rc = evaluate_rational(PC, QC, y2); rs = evaluate_rational(PS, QS, y2); - factor = sqrt(2 / (x * pi<T>())); - value = factor * (rc * sin(z) + y * rs * cos(z)); + factor = constants::one_div_root_pi<T>() / sqrt(x); + // + // The following code is really just: + // + // T z = x - 0.25f * pi<T>(); + // value = factor * (rc * sin(z) + y * rs * cos(z)); + // + // But using the sin/cos addition formulae and constant values for + // sin/cos of PI/4 which then cancel part of the "factor" term as they're all + // 1 / sqrt(2): + // + T sx = sin(x); + T cx = cos(x); + value = factor * (rc * (sx - cx) + y * rs * (cx + sx)); } return value; |