From: Gavin Kistner <gavin@...>
Date: 2005-09-19T22:23:43+09:00
Subject: Re: Capcha in ruby

On Sep 19, 2005, at 7:11 AM, Robbie Carlton wrote:
> I like the maths question idea. Is there any set of enumerable  
> problems that
> would cause a human no difficulties, for which there isn't a general
> solution algorithm?
> I realise this is a maths question, but just wondered if anyone had  
> any
> thoughts.

Well, taking that thought further, you could even keep simpletons (or  
at least those bad at math) out of your site, by setting your  
question difficulty to an appropriate level.

"Type the number that comes right before seventy-five."

"What is fifteen plus twelve minus six?"

"What is six x minus three q, if q is two and x three?"

"What is two squared, cubed?"

"Is the cosine of zero one or zero?"

"What trigonometric function of an angle of a right triangle yields  
the ratio of the adjacent side's length divided by the hypotenuse?"

"What is the derivative of 2x^2, when x is 3?"

"What is the dot product of the vectors [4 7] and [3 4]?"

"What is the cross product of the vectors [4 7] and [3 4]?"

...and I'll stop there, before I embarrass myself trying to come up  
with tougher questions.