diff --git a/doc/scale-to-frequency.ipynb b/doc/scale-to-frequency.ipynb
index 1f45a31..5c65659 100644
--- a/doc/scale-to-frequency.ipynb
+++ b/doc/scale-to-frequency.ipynb
@@ -44,7 +44,7 @@
     ">\n",
     ">   The child function at scale $s$ is\n",
     ">\n",
-    ">   $\\Psi_{s,x}(t) = \\frac{1}{\\sqrt{s} } \\frac{\\Psi(t-x)}{s}$\n",
+    ">   $\\Psi_{s,x}(t) = \\frac{1}{\\sqrt{s} } \\Psi(\\frac{t-x}{s})$\n",
     ">\n",
     ">   where $x$ is the shift parameter used to convolve the signal being analysed with the wavelet.\n",
     "\n",