diff --git a/docs/source/methods/neutron_physics.rst b/docs/source/methods/neutron_physics.rst
index bea92f992..f1b0a5bde 100644
--- a/docs/source/methods/neutron_physics.rst
+++ b/docs/source/methods/neutron_physics.rst
@@ -1403,7 +1403,7 @@ given analytically by
 .. math::
     :label: coherent-elastic-angle
 
-    \mu = 1 - \frac{E_i}{E}
+    \mu = 1 - \frac{2E_i}{E}
 
 where :math:`E_i` is the energy of the Bragg edge that scattered the neutron.