Mathematics desk
< December 13	<< Nov \| December \| Jan >>	December 15 >

Welcome to the Wikipedia Mathematics Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

December 14[edit]

The Laplacian[edit]

For the Laplacian operator, should one use Δ (U+0394: GREEK CAPITAL LETTER DELTA) or ∆ (U+2206: INCREMENT)? --Andreas Rejbrand (talk) 11:27, 14 December 2012 (UTC)[reply]

The Unicode standard lists under U+2206: INCREMENT = Laplace operator, but makes no such reference under U+0394. From this I would take it that U+2206 is the appropriate character to use. — Quondum 12:20, 14 December 2012 (UTC)[reply]

Thank you for your reply. I had made the same observation, so I'd guess this is correct. --Andreas Rejbrand (talk) 20:10, 14 December 2012 (UTC)[reply]

Resolved

sequence which is not in any l^p[edit]

Find a sequence which converges to 0 but not in any l^p ,where p>=1.Is this sequence 1/ln(n+1) or 1/(n^1/p)plz help me to understand it.. — Preceding unsigned comment added by 182.187.28.118 (talk) 12:00, 14 December 2012 (UTC)[reply]

It's the former. "Not in any l^p" means you first choose the sequence and then for any p you choose it will not be in l^p. You can't refer to p itself when choosing the function. -- Meni Rosenfeld (talk) 12:56, 14 December 2012 (UTC)[reply]

Am I right?[edit]

3cos4x * 4 = 12cos4x? --84.110.173.27 (talk) 17:51, 14 December 2012 (UTC)[reply]

Ambiguous as written. It depends on where you put the parens:

3(cos4x) * 4 = 12(cos4x)

3cos(4x) * 4 = 12cos(4x)

3cos(4x * 4) ≠ 12cos(4x)

StuRat (talk) 17:54, 14 December 2012 (UTC)[reply]

thanks, 1. what the difference between: 12cos(4x) to 12(cos4x)?

2. y' (3sin4x) = 4*3sinx = 12cos4x right? --84.110.173.27 (talk) 09:38, 15 December 2012 (UTC)[reply]

1: No difference. They both mean 12 ⋅ (cos(4x)), and may also be written 12 cos 4x.

2: Reading between the lines, you mean: "y = 3 sin 4x, so y′ = 4 ⋅ 3 cos 4x = 12 cos 4x, right?", to which the answer is "Yes, if by the prime you mean the derivative with respect to x". — Quondum 10:21, 15 December 2012 (UTC)[reply]