MHB A mistake in the wolfram mathworld website

[alyafey22]

I was proving a formula for the hypergoemtric function and noticed that there is a mistake in the following page look at equation (1) and compare it to equation (16) in the following page . Is there a way to correct the mistake ?

 

[mathbalarka]

I often come up with a whole lot of mistakes on that particular site.

Look at the leftmost edge of the page and you'll see a tool to send message to the editorial board. Quote the line you feel is incorrect, then send them that.

 

[Sudharaka]

I was proving a formula for the hypergoemtric function and noticed that there is a mistake in the following page look at equation (1) and compare it to equation (16) in the following page . Is there a way to correct the mistake ?

Hi Zaid, :)

Both of your links refer to the same page. :)

 

[alyafey22]

Hi Zaid, :)

Both of your links refer to the same page. :)

Oops , sorry for that , I edited it.

 

[topsquark]

Hey, WolframAlpha still thinks that the integral of 1/x is log(x).

-Dan

 

[I like Serena]

Hey, WolframAlpha still thinks that the integral of 1/x is log(x).

-Dan

What's wrong with that? ;)

Actually W|A gives $\log(x) + \color{gray}{\text{constant}}$.
And isn't that true for all $x>0$? It's not as if W|A gives a domain.
Isn't it also true for all $x \in \mathbb C^*$?
Anyway, even in the real numbers it is properly:
\begin{cases}\ln x + C_1 & \text{if } x>0 \\ \ln(-x) + C_2 & \text{if } x<0 \end{cases}

I think that W|A prefers complex numbers, or otherwise would probably still not give such a convoluted answer.

 

[polygamma]

You have to somehow tell Wolfram Alpha that $x$ is a real variable. Otherwise it will assume that $x$ is a complex variable. And if $x$ is a complex variable, $\displaystyle \int \frac{1}{x} \ dz = \log(x) + C$ is a true statement.

 

[topsquark]

You have to somehow tell Wolfram Alpha that $x$ is a real variable. Otherwise it will assume that $x$ is a complex variable. And if $x$ is a complex variable, $\displaystyle \int \frac{1}{x} \ dz = \log(x) + C$ is a true statement.

Good point. Not to hijack the thread but can you quickly tell me how you would tell Wolfram x is real?

-Dan

 

[polygamma]

For whatever reason, I am unable to link directly to the Wolfram Alpha output.

But the following command seems to return nonsense.

assuming[Element[x, Reals] , int [1/x,x]]

 

[Sawarnik]

I often come up with a whole lot of mistakes on that particular site.

Look at the leftmost edge of the page and you'll see a tool to send message to the editorial board. Quote the line you feel is incorrect, then send them that.

Yeah, right. An awful lot of mistakes. I once tried that send message and sent the error and correction but no one looked at it, and remains incorrect today as well, and so I think its useless. In fact, I think Wikipedia is less error-prone than Mathworld.

 

[I like Serena]

Yeah, right. An awful lot of mistakes. I once tried that send message and sent the error and correction but no one looked at it, and remains incorrect today as well, and so I think its useless. In fact, I think Wikipedia is less error-prone than Mathworld.

Which mistake?

 

[Sawarnik]

Which mistake?

One that I found recently: Semiperimeter -- from Wolfram MathWorld

 

[I like Serena]

One that I found recently: Semiperimeter -- from Wolfram MathWorld

So where is the mistake in that article?

 

[Sawarnik]

So where is the mistake in that article?

"and Brahmagupta's formula for the area of a quadrilateral:"

Is the formula after that Brahmagupta's!

 

[Saitama]

"and Brahmagupta's formula for the area of a quadrilateral:"

Is that formula after that Brahmagupta's!

Erm...it is.

Brahmagupta's formula - Wikipedia, the free encyclopedia

 

[Sawarnik]

Erm...it is.

Brahmagupta's formula - Wikipedia, the free encyclopedia

Seriously? Look carefully.

It is Bretschneider's formula - Wikipedia, the free encyclopedia.

 

[Saitama]

It is Bretschneider's formula - Wikipedia, the free encyclopedia.

Yep, sorry, the wikipedia article I linked to also states that it is Bretschneider's formula.

 

[I like Serena]

Hmm, so the math is perfectly correct and as such MathWorld is reliable.
The problem is that the credits given are not correct in that article.
Just now, I have sent a contribution to MathWorld with the suggestion to correct this.
We'll see.

 

[mathbalarka]

Hmm, so the math is perfectly correct and as such MathWorld is reliable.

At least, more than wikipedia in any case.

 

[I like Serena]

At least, more than wikipedia in any case.

I'll bite.
Where is the mistake in wikipedia?

 

[mathbalarka]

Where is the mistake in wikipedia?

Somehow, I knew you'd say that. There have been many changes in wiki since I saw them, so I will show you only the ones I can find.

First, I remember wiki giving a terribly false estimate for the totient sum

$$\sum_{n\leq x} \frac1{\varphi(n)}$$

Which I don't remember what it was and they corrected it afterwards, as I see it.

Second is something on tetration, I haven't seen whether it is still there but I can't rember it either.

The last is Von Mangoldt. It's fresh as new and you can see all the craps there if you open the page up.

 

[Sawarnik]

Hmm, so the math is perfectly correct and as such MathWorld is reliable.
The problem is that the credits given are not correct in that article.
Just now, I have sent a contribution to MathWorld with the suggestion to correct this.
We'll see.

No, the formula named is wrong, which is problematic.
And I had already sent a message to them, but there has been no corrections!

- - - Updated - - -

At least, more than wikipedia in any case.

But you can correct errors in Wiki with no prob. The MathWorld team however never listens to any suggestion and the mistake remain mistakes.

But form my experience Wiki is not at all as bad as people say.