Update equation

docs/examples/bunching.ipynb

@@ -9,7 +9,8 @@
     "\n",
     "Bunching at some wavelength $\\lambda$ for a list of particles $z$ is given by the weighted sum of complex phasors:\n",
     "\n",
-    "$$B(z, \\lambda) = \\frac{\\left|\\sum_j w_j e^{i k z_j}\\right|}{\\sum w_j}$$\n",
+    "$$B(z, \\lambda) \\equiv \\frac{\\left|\\sum_j w_j e^{i k z_j}\\right|}{\\sum w_j}\n",
+    "$$\n",
     "\n",
     "where $k = 2\\pi/\\lambda$ and $w_j$ are the weights of the particles.\n",
     "\n",