180 \cdot \frac{\tan^{-1} \left(\frac{\left(\frac{\frac{{\left(a \cdot \cos \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2} + {\left(b \cdot \sin \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2}}{y-scale}}{y-scale} - \frac{\frac{{\left(a \cdot \sin \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2} + {\left(b \cdot \cos \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2}}{x-scale}}{x-scale}\right) - \sqrt{{\left(\frac{\frac{{\left(a \cdot \sin \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2} + {\left(b \cdot \cos \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2}}{x-scale}}{x-scale} - \frac{\frac{{\left(a \cdot \cos \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2} + {\left(b \cdot \sin \left(\frac{angle}{180} \cdot \pi\right)\right)}^{2}}{y-scale}}{y-scale}\right)}^{2} + {\left(\frac{\frac{\left(\left(2 \cdot \left({b}^{2} - {a}^{2}\right)\right) \cdot \sin \left(\frac{angle}{180} \cdot \pi\right)\right) \cdot \cos \left(\frac{angle}{180} \cdot \pi\right)}{x-scale}}{y-scale}\right)}^{2}}}{\frac{\frac{\left(\left(2 \cdot \left({b}^{2} - {a}^{2}\right)\right) \cdot \sin \left(\frac{angle}{180} \cdot \pi\right)\right) \cdot \cos \left(\frac{angle}{180} \cdot \pi\right)}{x-scale}}{y-scale}}\right)}{\pi}
\begin{array}{l}
t_0 := 1 - 1.54320987654321 \cdot 10^{-05} \cdot {\left(angle \cdot \pi\right)}^{2}\\
t_1 := \frac{angle}{180} \cdot \pi\\
t_2 := \sin t_1\\
t_3 := {\left(b \cdot t_2\right)}^{2}\\
t_4 := {\left(a \cdot t_2\right)}^{2}\\
t_5 := \frac{\frac{{a}^{2} + t_3}{y-scale}}{y-scale}\\
t_6 := \cos t_1\\
t_7 := \frac{\frac{t_4 + {\left(b \cdot t_6\right)}^{2}}{x-scale}}{x-scale}\\
t_8 := \frac{\frac{t_6 \cdot \left(t_2 \cdot \left(2 \cdot \left({b}^{2} - {a}^{2}\right)\right)\right)}{x-scale}}{y-scale}\\
t_9 := {t_8}^{2}\\
t_10 := \sqrt{{\left(t_7 - \frac{\frac{t_3 + {\left(a \cdot t_6\right)}^{2}}{y-scale}}{y-scale}\right)}^{2} + t_9}\\
\mathbf{if}\;\frac{angle}{180} \leq -1.679018559483575 \cdot 10^{+88}:\\
\;\;\;\;180 \cdot \frac{\tan^{-1} \left(\frac{\left(t_5 - \frac{\frac{t_4 + {\left(b \cdot t_0\right)}^{2}}{x-scale}}{x-scale}\right) - t_10}{t_8}\right)}{\pi}\\
\mathbf{elif}\;\frac{angle}{180} \leq 7.852683309522566 \cdot 10^{+196}:\\
\;\;\;\;180 \cdot \frac{\tan^{-1} \left(\frac{\left(\frac{\frac{t_3 + {\left(a \cdot t_0\right)}^{2}}{y-scale}}{y-scale} - t_7\right) - \sqrt{t_9 + {\left(t_7 - t_5\right)}^{2}}}{t_8}\right)}{\pi}\\
\mathbf{else}:\\
\;\;\;\;180 \cdot \frac{\tan^{-1} \left(\frac{\left(t_5 - t_7\right) - t_10}{t_8}\right)}{\pi}\\
\end{array}
(FPCore (a b angle x-scale y-scale)
:precision binary64
(*
180.0
(/
(atan
(/
(-
(-
(/
(/
(+
(pow (* a (cos (* (/ angle 180.0) PI))) 2.0)
(pow (* b (sin (* (/ angle 180.0) PI))) 2.0))
y-scale)
y-scale)
(/
(/
(+
(pow (* a (sin (* (/ angle 180.0) PI))) 2.0)
(pow (* b (cos (* (/ angle 180.0) PI))) 2.0))
x-scale)
x-scale))
(sqrt
(+
(pow
(-
(/
(/
(+
(pow (* a (sin (* (/ angle 180.0) PI))) 2.0)
(pow (* b (cos (* (/ angle 180.0) PI))) 2.0))
x-scale)
x-scale)
(/
(/
(+
(pow (* a (cos (* (/ angle 180.0) PI))) 2.0)
(pow (* b (sin (* (/ angle 180.0) PI))) 2.0))
y-scale)
y-scale))
2.0)
(pow
(/
(/
(*
(*
(* 2.0 (- (pow b 2.0) (pow a 2.0)))
(sin (* (/ angle 180.0) PI)))
(cos (* (/ angle 180.0) PI)))
x-scale)
y-scale)
2.0))))
(/
(/
(*
(* (* 2.0 (- (pow b 2.0) (pow a 2.0))) (sin (* (/ angle 180.0) PI)))
(cos (* (/ angle 180.0) PI)))
x-scale)
y-scale)))
PI)))(FPCore (a b angle x-scale y-scale)
:precision binary64
(let* ((t_0 (- 1.0 (* 1.54320987654321e-05 (pow (* angle PI) 2.0))))
(t_1 (* (/ angle 180.0) PI))
(t_2 (sin t_1))
(t_3 (pow (* b t_2) 2.0))
(t_4 (pow (* a t_2) 2.0))
(t_5 (/ (/ (+ (pow a 2.0) t_3) y-scale) y-scale))
(t_6 (cos t_1))
(t_7 (/ (/ (+ t_4 (pow (* b t_6) 2.0)) x-scale) x-scale))
(t_8
(/
(/ (* t_6 (* t_2 (* 2.0 (- (pow b 2.0) (pow a 2.0))))) x-scale)
y-scale))
(t_9 (pow t_8 2.0))
(t_10
(sqrt
(+
(pow
(- t_7 (/ (/ (+ t_3 (pow (* a t_6) 2.0)) y-scale) y-scale))
2.0)
t_9))))
(if (<= (/ angle 180.0) -1.679018559483575e+88)
(*
180.0
(/
(atan
(/
(- (- t_5 (/ (/ (+ t_4 (pow (* b t_0) 2.0)) x-scale) x-scale)) t_10)
t_8))
PI))
(if (<= (/ angle 180.0) 7.852683309522566e+196)
(*
180.0
(/
(atan
(/
(-
(- (/ (/ (+ t_3 (pow (* a t_0) 2.0)) y-scale) y-scale) t_7)
(sqrt (+ t_9 (pow (- t_7 t_5) 2.0))))
t_8))
PI))
(* 180.0 (/ (atan (/ (- (- t_5 t_7) t_10) t_8)) PI))))))double code(double a, double b, double angle, double x_45_scale, double y_45_scale) {
return 180.0 * (atan((((((pow((a * cos((angle / 180.0) * ((double) M_PI))), 2.0) + pow((b * sin((angle / 180.0) * ((double) M_PI))), 2.0)) / y_45_scale) / y_45_scale) - (((pow((a * sin((angle / 180.0) * ((double) M_PI))), 2.0) + pow((b * cos((angle / 180.0) * ((double) M_PI))), 2.0)) / x_45_scale) / x_45_scale)) - sqrt(pow(((((pow((a * sin((angle / 180.0) * ((double) M_PI))), 2.0) + pow((b * cos((angle / 180.0) * ((double) M_PI))), 2.0)) / x_45_scale) / x_45_scale) - (((pow((a * cos((angle / 180.0) * ((double) M_PI))), 2.0) + pow((b * sin((angle / 180.0) * ((double) M_PI))), 2.0)) / y_45_scale) / y_45_scale)), 2.0) + pow((((((2.0 * (pow(b, 2.0) - pow(a, 2.0))) * sin((angle / 180.0) * ((double) M_PI))) * cos((angle / 180.0) * ((double) M_PI))) / x_45_scale) / y_45_scale), 2.0))) / (((((2.0 * (pow(b, 2.0) - pow(a, 2.0))) * sin((angle / 180.0) * ((double) M_PI))) * cos((angle / 180.0) * ((double) M_PI))) / x_45_scale) / y_45_scale)) / ((double) M_PI));
}
double code(double a, double b, double angle, double x_45_scale, double y_45_scale) {
double t_0 = 1.0 - (1.54320987654321e-05 * pow((angle * ((double) M_PI)), 2.0));
double t_1 = (angle / 180.0) * ((double) M_PI);
double t_2 = sin(t_1);
double t_3 = pow((b * t_2), 2.0);
double t_4 = pow((a * t_2), 2.0);
double t_5 = ((pow(a, 2.0) + t_3) / y_45_scale) / y_45_scale;
double t_6 = cos(t_1);
double t_7 = ((t_4 + pow((b * t_6), 2.0)) / x_45_scale) / x_45_scale;
double t_8 = ((t_6 * (t_2 * (2.0 * (pow(b, 2.0) - pow(a, 2.0))))) / x_45_scale) / y_45_scale;
double t_9 = pow(t_8, 2.0);
double t_10 = sqrt(pow((t_7 - (((t_3 + pow((a * t_6), 2.0)) / y_45_scale) / y_45_scale)), 2.0) + t_9);
double tmp;
if ((angle / 180.0) <= -1.679018559483575e+88) {
tmp = 180.0 * (atan(((t_5 - (((t_4 + pow((b * t_0), 2.0)) / x_45_scale) / x_45_scale)) - t_10) / t_8) / ((double) M_PI));
} else if ((angle / 180.0) <= 7.852683309522566e+196) {
tmp = 180.0 * (atan((((((t_3 + pow((a * t_0), 2.0)) / y_45_scale) / y_45_scale) - t_7) - sqrt(t_9 + pow((t_7 - t_5), 2.0))) / t_8) / ((double) M_PI));
} else {
tmp = 180.0 * (atan(((t_5 - t_7) - t_10) / t_8) / ((double) M_PI));
}
return tmp;
}



Bits error versus a



Bits error versus b



Bits error versus angle



Bits error versus x-scale



Bits error versus y-scale
Results
if (/.f64 angle 180) < -1.67901855948357504e88Initial program 59.2
Taylor expanded around 0 57.7
Simplified57.7
Taylor expanded around 0 57.7
if -1.67901855948357504e88 < (/.f64 angle 180) < 7.85268330952256606e196Initial program 53.6
Taylor expanded around 0 53.9
Simplified53.9
Taylor expanded around 0 53.9
if 7.85268330952256606e196 < (/.f64 angle 180) Initial program 58.9
Taylor expanded around 0 58.9
Final simplification55.0
herbie shell --seed 2021190
(FPCore (a b angle x-scale y-scale)
:name "raw-angle from scale-rotated-ellipse"
:precision binary64
(* 180.0 (/ (atan (/ (- (- (/ (/ (+ (pow (* a (cos (* (/ angle 180.0) PI))) 2.0) (pow (* b (sin (* (/ angle 180.0) PI))) 2.0)) y-scale) y-scale) (/ (/ (+ (pow (* a (sin (* (/ angle 180.0) PI))) 2.0) (pow (* b (cos (* (/ angle 180.0) PI))) 2.0)) x-scale) x-scale)) (sqrt (+ (pow (- (/ (/ (+ (pow (* a (sin (* (/ angle 180.0) PI))) 2.0) (pow (* b (cos (* (/ angle 180.0) PI))) 2.0)) x-scale) x-scale) (/ (/ (+ (pow (* a (cos (* (/ angle 180.0) PI))) 2.0) (pow (* b (sin (* (/ angle 180.0) PI))) 2.0)) y-scale) y-scale)) 2.0) (pow (/ (/ (* (* (* 2.0 (- (pow b 2.0) (pow a 2.0))) (sin (* (/ angle 180.0) PI))) (cos (* (/ angle 180.0) PI))) x-scale) y-scale) 2.0)))) (/ (/ (* (* (* 2.0 (- (pow b 2.0) (pow a 2.0))) (sin (* (/ angle 180.0) PI))) (cos (* (/ angle 180.0) PI))) x-scale) y-scale))) PI)))