\[\frac{1 - \tan x \cdot \tan x}{1 + \tan x \cdot \tan x}\]

\frac{1 - \tan x \cdot \tan x}{1 + \tan x \cdot \tan x}

double f(double x) {
        double r7971 = 1.0;
        double r7972 = x;
        double r7973 = tan(r7972);
        double r7974 = r7973 * r7973;
        double r7975 = r7971 - r7974;
        double r7976 = r7971 + r7974;
        double r7977 = r7975 / r7976;
        return r7977;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019191 
(FPCore (x)
  :name "Trigonometry B"
  (/ (- 1.0 (* (tan x) (tan x))) (+ 1.0 (* (tan x) (tan x)))))

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