\[\frac{2 + \left(\left(\sqrt{2} \cdot \left(\sin x - \frac{\sin y}{16}\right)\right) \cdot \left(\sin y - \frac{\sin x}{16}\right)\right) \cdot \left(\cos x - \cos y\right)}{3 \cdot \left(\left(1 + \frac{\sqrt{5} - 1}{2} \cdot \cos x\right) + \frac{3 - \sqrt{5}}{2} \cdot \cos y\right)}\]

\frac{2 + \left(\left(\sqrt{2} \cdot \left(\sin x - \frac{\sin y}{16}\right)\right) \cdot \left(\sin y - \frac{\sin x}{16}\right)\right) \cdot \left(\cos x - \cos y\right)}{3 \cdot \left(\left(1 + \frac{\sqrt{5} - 1}{2} \cdot \cos x\right) + \frac{3 - \sqrt{5}}{2} \cdot \cos y\right)}

double f(double x, double y) {
        double r8276 = 2.0;
        double r8277 = sqrt(r8276);
        double r8278 = x;
        double r8279 = sin(r8278);
        double r8280 = y;
        double r8281 = sin(r8280);
        double r8282 = 16.0;
        double r8283 = r8281 / r8282;
        double r8284 = r8279 - r8283;
        double r8285 = r8277 * r8284;
        double r8286 = r8279 / r8282;
        double r8287 = r8281 - r8286;
        double r8288 = r8285 * r8287;
        double r8289 = cos(r8278);
        double r8290 = cos(r8280);
        double r8291 = r8289 - r8290;
        double r8292 = r8288 * r8291;
        double r8293 = r8276 + r8292;
        double r8294 = 3.0;
        double r8295 = 1.0;
        double r8296 = 5.0;
        double r8297 = sqrt(r8296);
        double r8298 = r8297 - r8295;
        double r8299 = r8298 / r8276;
        double r8300 = r8299 * r8289;
        double r8301 = r8295 + r8300;
        double r8302 = r8294 - r8297;
        double r8303 = r8302 / r8276;
        double r8304 = r8303 * r8290;
        double r8305 = r8301 + r8304;
        double r8306 = r8294 * r8305;
        double r8307 = r8293 / r8306;
        return r8307;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019191 
(FPCore (x y)
  :name "Diagrams.TwoD.Path.Metafont.Internal:hobbyF from diagrams-contrib-1.3.0.5"
  (/ (+ 2.0 (* (* (* (sqrt 2.0) (- (sin x) (/ (sin y) 16.0))) (- (sin y) (/ (sin x) 16.0))) (- (cos x) (cos y)))) (* 3.0 (+ (+ 1.0 (* (/ (- (sqrt 5.0) 1.0) 2.0) (cos x))) (* (/ (- 3.0 (sqrt 5.0)) 2.0) (cos y))))))

Backtrace

get-representation: Unknown representation #f		L	C
loop	/data/pavpan/nightlies/herbie/interface2/src/points.rkt	122	4
prepare-points	/data/pavpan/nightlies/herbie/interface2/src/points.rkt	146	0
setup-prog!34	/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt	67	0
run-improve43	/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt	339	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28