4 files changed, 5 insertions, 10 deletions
diff --git a/src/likelihood.c b/src/likelihood.c
index 587349b..17cde5d 100644
--- a/src/likelihood.c
+++ b/src/likelihood.c
@@ -603,7 +603,7 @@ static void get_expected_charge(double beta, double theta0, double *pos, double
      * pretty low, this is expected to be a very small effect. */
     prob_sct = 1.0 - get_fsct_d2o(l_d2o)*get_fsct_h2o(l_h2o)*get_fsct_acrylic(AV_THICKNESS);
 
-    charge = omega*FINE_STRUCTURE_CONSTANT*z*z*(1-(1/(beta*beta*n*n)))*get_probability(beta, cos_theta, theta0);
+    charge = omega*FINE_STRUCTURE_CONSTANT*z*z*(1-(1/(beta*beta*n*n)))*get_probability(beta, cos_theta, sin_theta, theta0);
 
     *reflected = (1.0-prob_abs)*(1.0-prob_sct)*f_reflec*charge + prob_sct*charge;
 
diff --git a/src/scattering.c b/src/scattering.c
index 25b17d4..2512cda 100644
--- a/src/scattering.c
+++ b/src/scattering.c
@@ -191,14 +191,8 @@ void init_interpolation(void)
     gsl_integration_cquad_workspace_free(w);
 }
 
-double get_probability(double beta, double cos_theta, double theta0)
+double get_probability(double beta, double cos_theta, double sin_theta, double theta0)
 {
-    double sin_theta;
-
-    /* Technically this isn't defined up to a sign, but it doesn't matter since
-     * we are going to square it everywhere. */
-    sin_theta = sqrt(1-pow(cos_theta,2));
-
     /* Make sure theta0 is less than MAX_THETA0, otherwise it's possible that
      * gsl_spline2d_eval() will quit. */
     if (theta0 > MAX_THETA0) theta0 = MAX_THETA0;
diff --git a/src/scattering.h b/src/scattering.h
index 265f653..43e59f7 100644
--- a/src/scattering.h
+++ b/src/scattering.h
@@ -23,7 +23,7 @@
 #define MAX_THETA0 1.0
 
 void init_interpolation(void);
-double get_probability(double beta, double cos_theta, double theta0);
+double get_probability(double beta, double cos_theta, double sin_theta, double theta0);
 double get_probability2(double beta);
 double get_weighted_quantum_efficiency(void);
 void free_interpolation(void);
diff --git a/src/test-likelihood.c b/src/test-likelihood.c
index 5bb7788..497a6eb 100644
--- a/src/test-likelihood.c
+++ b/src/test-likelihood.c
@@ -189,7 +189,8 @@ int main(int argc, char **argv)
         double lo, hi;
         gsl_histogram_get_range(h, i, &lo, &hi);
         double cos_theta = (lo+hi)/2.0;
-        h->bin[i] = get_probability(beta, cos_theta, theta0);
+        double sin_theta = sqrt(1-cos_theta*cos_theta);
+        h->bin[i] = get_probability(beta, cos_theta, sin_theta, theta0);
     }
 
     free_interpolation();