Updated PCA to have more notation

Author: Michael Galarnyk

.DS_Store

@@ -2539,7 +2539,7 @@
     "\n",
     "$sigma = \\frac{1}{K}\\sum_{k=1}^{K}\\left(  x^{(k)}-\\bar{x}\\right)\\left(  x^{(k)}-\\bar{x}\\right)^{T}.$\n",
     "\n",
-    "Some people use k-1 instead of k for [bessels correction](https://en.wikipedia.org/wiki/Bessel%27s_correction)\n",
+    "Some people use K-1 instead of K for [bessels correction](https://en.wikipedia.org/wiki/Bessel%27s_correction)\n",
     "\n",
     "where $\\mathbf{\\bar{x}}$ is the mean vector \n",
     "$\\mathbf{\\bar{x}} = \\frac{1}{K}\\sum\\limits_{k=1}^K x^{(k)}.$  \n",