add include? method on arrays

ruby.html.markdown

@@ -169,6 +169,9 @@ array[1..3] #=> [2, 3, 4]
 # Add to an array like this
 array << 6 #=> [1, 2, 3, 4, 5, 6]
 
+# Check if an item exists in an array
+array.include?(1) #=> true
+
 # Hashes are Ruby's primary dictionary with keys/value pairs.
 # Hashes are denoted with curly braces:
 hash = { 'color' => 'green', 'number' => 5 }