[Tutor] calculate area of a circle

[mbikinyi brat]

Hi All, 
This is a code I have written to calculate the area of a circle.
def area(radius):
 temp=math.pi*radius**2
 return temp
 
I now call it by entering area(12) at the prompt in IDLE. This is the error message I get. Can someone help please?
Traceback (most recent call last):
  File "<pyshell#22>", line 1, in <module>
    area(10)
  File "<pyshell#21>", line 2, in area
    temp=math.pi*radius**2
NameError: global name 'math' is not defined
 
Regards,
Henry
 


      
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