diff --git a/exercises/Exercise3.ipynb b/exercises/Exercise3.ipynb
index a1c66ae..f99d862 100644
--- a/exercises/Exercise3.ipynb
+++ b/exercises/Exercise3.ipynb
@@ -37,7 +37,7 @@
     "For any single qubit superposition $|\\psi\\rangle = c_0 |0\\rangle + c_1 |1\\rangle$,\n",
     "\n",
     "$\n",
-    "\\langle \\sigma^x \\rangle^2 + \\langle \\sigma^y \\rangle^2 + c^2 = 1\n",
+    "\\langle \\sigma^x \\rangle^2 + \\langle \\sigma^y \\rangle^2 + \\langle \\sigma^z \\rangle^2 = 1\n",
     "$\n",
     "\n",
     "Verify this for the following states.\n",