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# What is 2''?

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Orikal    138
Could someone tell me what 2" means? I'd search for it, but no search engines recognize " . context: show that 2n = O (3n), but 2" does not equal big-Theta (3n) [edited by - Orikal on September 2, 2003 1:46:19 AM]

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Ravyne    14300
Second Dirivative.

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But that doesn't make sense when applied to a constant. To use a hypothetical example, if f = 3 * x^2, then f ' = 6x and f " = 6, meaning the second derivative of 3x^2 is 6. But 2' makes no sense.

~CGameProgrammer( );

[edited by - CGameProgrammer on September 2, 2003 1:31:12 AM]

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Orikal    138
quote:
Original post by CGameProgrammer
But 2' makes no sense.

lol, tell me about it. I'm beginning to think it's some weird notation that the author of my textbook invented. Guess I'm not going to get much credit for that problem.

[edited by - Orikal on September 2, 2003 1:45:42 AM]

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Is there any chance the 2" was actually 2n where the top of the n was cut off in the photocopy or scan or bad printing?

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Orikal    138
Nah, it''s very clearly a double-prime and someone asked about it in class. Too bad I wasn''t paying much attention at the time.

I think I''m going to assume 2n for its meaning, though, cuz that makes the most sense.

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if it is 2'''', it might just give the answer of 0...

2'' = 0
0'' = 0

... dunno...

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Sander    1332
Two inch perhaps??

Sander Maréchal

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Guest Anonymous Poster
yeah, 2" = 2 inches, 2'' = 2 foot

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Guest Anonymous Poster
2 to the power of 11?

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Cedric    158
What is big-Theta? What kind of course is this? Algorithms?

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capn_midnight    1707
it could still be a typographical error. I''ve seen completely different superscripts on such things before.

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Orikal    138
quote:
Original post by Cedric
What is big-Theta? What kind of course is this? Algorithms?

So far, the course is an extension of discrete mathematics that uses mathematical proofs and graph theory to model automata that can inerpret languages described by respective grammars. Say that ten times fast.

We''re using An Introduction to Formal Languages and Automata by Peter Linz, which is where this weird 2" thing came from. I should have asked what it meant in class this morning, but I forgot.

Big-Theta and O (big-O) are functions that compare the growth rate of two functions. Ex. 2n = O (3n) basically means that 3n will always be larger than 2n for sufficiently large values of n .

And yes, one of big-Theta''s applications is analyzing the efficiency of algorithms.

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rypyr    252
I think it''s a superscript ''n'' with its top lopped off...just a guess...

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Fruny    1658
The exercise appears to be on the distinction between O and Θ, so I''d be inclined to think it is 2n.

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Doc    586
quote:
Original post by Anonymous Poster
yeah, 2" = 2 inches, 2'' = 2 foot

Along that completely out-of-context line:
2'''' may also mean 2 seconds, as in degrees-minutes-seconds.

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It''s gotta be 2n. After all, it is true that
2n == O(3n)but2n != BigTheta(3n)
On the other hand it is also true if it is 211 or the second derivative of 2 (with respect to anything). We can however say that it isn''t inches or seconds of an arc because these are not real numbers!
Progress!

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GameCat    292
If the course is on formal languages it might be some weird string notation. All books I''ve seen use e.g. k* for k repeated 0 to n times where n is any natural number, but it''s possible your book has it''s own notation. That doesn''t make any sense given the context though, it doesn''t relate to big o or theta at all.