diff --git a/scicalc b/scicalc
index 1667b1d..91e40f2 100755
--- a/scicalc
+++ b/scicalc
@@ -2,8 +2,8 @@
 #
 # A simple command-line scientific calculator.
 #
-
 import sys, math
+import numpy as np
 
 def die_with_usage(message):
 	print("\n****\n**** error: {}\n****\n".format(message), file=sys.stderr)
@@ -47,6 +47,12 @@ def log10(x):
 	"""Return a base-10 logarithm of x"""
 	
 	return math.log10(x)
+    
+def tan(x):
+    """Return the value of tan(x)"""
+    
+    return np.tan(x)
+
 
 #
 # The dictionary that maps the command-line name of the operation,
@@ -58,6 +64,7 @@ operators = {
 	'sum': add,
 	'mul': mul,
 	'log10': log10,
+    	'tan': tan,
 }
 
 if __name__ == "__main__":