\left(\left(2 \cdot \left({b}^{2} - {a}^{2}\right)\right) \cdot \sin \left(\pi \cdot \frac{angle}{180}\right)\right) \cdot \cos \left(\pi \cdot \frac{angle}{180}\right)
\begin{array}{l}
t_0 := \pi \cdot \frac{angle}{180}\\
t_1 := \cos t_0\\
\left(\left(2 \cdot \left({b}^{2} - {a}^{2}\right)\right) \cdot \mathsf{expm1}\left(\mathsf{log1p}\left(\sin t_0\right)\right)\right) \cdot \sqrt[3]{t_1 \cdot \left(t_1 \cdot t_1\right)}
\end{array}
(FPCore (a b angle) :precision binary64 (* (* (* 2.0 (- (pow b 2.0) (pow a 2.0))) (sin (* PI (/ angle 180.0)))) (cos (* PI (/ angle 180.0)))))
(FPCore (a b angle)
:precision binary64
(let* ((t_0 (* PI (/ angle 180.0))) (t_1 (cos t_0)))
(*
(* (* 2.0 (- (pow b 2.0) (pow a 2.0))) (expm1 (log1p (sin t_0))))
(cbrt (* t_1 (* t_1 t_1))))))double code(double a, double b, double angle) {
return ((2.0 * (pow(b, 2.0) - pow(a, 2.0))) * sin(((double) M_PI) * (angle / 180.0))) * cos(((double) M_PI) * (angle / 180.0));
}
double code(double a, double b, double angle) {
double t_0 = ((double) M_PI) * (angle / 180.0);
double t_1 = cos(t_0);
return ((2.0 * (pow(b, 2.0) - pow(a, 2.0))) * expm1(log1p(sin(t_0)))) * cbrt(t_1 * (t_1 * t_1));
}



Bits error versus a



Bits error versus b



Bits error versus angle
Results
Initial program 31.0
Applied add-cbrt-cube_binary6431.0
Applied expm1-log1p-u_binary6431.0
Final simplification31.0
herbie shell --seed 2022068
(FPCore (a b angle)
:name "ab-angle->ABCF B"
:precision binary64
(* (* (* 2.0 (- (pow b 2.0) (pow a 2.0))) (sin (* PI (/ angle 180.0)))) (cos (* PI (/ angle 180.0)))))