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Order symbol 
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#1
Nov2712, 01:26 PM

P: 127

Hi, I noticed in mathematics the O symbol is used in the following way:
A term T is in O(x^p), if lim x>0 T/x^p=c, for a constant c. While in computer science the O symbol is used is this way: A term T is in O(x^p), if lim x>∞ T/x^p is a constant. What gives, these two notations seem to be the complete opposite of each other? 


#2
Nov2712, 03:40 PM

Sci Advisor
P: 6,039

The O symbol is valid in both cases. It is up to you to define what the x limit is.



#3
Nov2812, 02:18 AM

P: 127

For example, in the first case x^7 is in O(x^5), but in the second case it is not. 


#4
Nov2812, 07:22 AM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,353

Order symbol
No, they are just two distinct cases of a general concept. We should aways say "f(x)= O(g(x)) as x> a and specify a. They are using two different values of a and so getting two different results.



#5
Nov2812, 07:57 AM

P: 127




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