Update theory.md (#172)

theory.md

@@ -46,6 +46,7 @@
 
 Supervised learning is a type of machine learning in which our algorithms are trained using well-labeled training data, and machines predict the output based on that data. Labeled data indicates that the input data has already been tagged with the appropriate output. Basically, it is the task of learning a function that maps the input set and returns an output. Some of its examples are: Linear Regression, Logistic Regression, KNN, etc.
 
+k-Nearest Neighbors(KNN):Looking at the k closest labeled data points 
 
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