Talk:Check Machin-like formulas: Difference between revisions
→Formulae hidden to most browsers by under-tested cosmetic edits on 24 July 2016
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:For example, dividing one by seven with <tt>1%7</tt> by default produces the float point approximation <tt>0.142857</tt>, but coercing extended precision with <tt>x: 1%7</tt> produces the exact ratio <tt>1r7</tt> (which is J's notation for rational numbers). J will carry exact values as far as it can through its computations; there are some built-in functions which have not been designed to produce exact results, and will revert to floating point values. Users have no control over these functions, and if they want a work-alike that produces exact results, they must write it themselves.
:--[[User:DanBron|DanBron]] 20:04, 20 December 2012 (UTC)
--[[User:Soegaard|Soegaard]] ([[User talk:Soegaard|talk]]) 12:34, 1 June 2013 (UTC)▼
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:::: Ah, that Zig-Zag explanation! For me it's an RC classic. One of the better bits of RC and its community that I remember fondly. Thanks again DanBron. --[[User:Paddy3118|Paddy3118]] 05:10, 22 December 2012 (UTC)
::::: Yes, that was a fun one. Good times, good times. Happy holidays Paddy3118, and to all my other RosettaComrades! --[[User:DanBron|DanBron]] 18:23, 22 December 2012 (UTC)
== Task is wrong ==
Proving that ''tan(x)=1'' is by no means a proof that ''x=pi/4''.
Thus, the sentence
''Verify the following Machin-like formulas are correct by calculating the value of tan(right hand side) for each equation using exact arithmetic and showing they equal 1:''
is just painfully wrong: this is '''not''' a verification that the equations are '''correct''', only that the RHS evaluates to ''pi/4 + k pi'', for some unknown integer ''k''.
▲
:Agreed that technically you also need to show that |RHS| < pi*3/4 to complete a formal proof, but since |arctan(x)| < |x| I would say that |RHS| < 2 is obvious by inspection of the denominators. I may reword the description to mention this [[User:TobyK|TobyK]] ([[User talk:TobyK|talk]])
::Yes, it's easy to amend :) [[User:Arbautjc|Arbautjc]] ([[User talk:Arbautjc|talk]]) 20:14, 1 May 2015 (UTC)
==Formulae hidden to most browsers by under-tested cosmetic edits on 24 July 2016 ==
Under-tested cosmetic edits made to the task page at and around 19:37, 24 July 2016, including the injection of spaces around expressions in <math> tags, have left some or all of the task description formulae completely invisible to all browsers which display the graphic file version of formulae rather than processing the MathML (this is, in fact, the majority of browsers). The MediaWiki processor does not currently expect such spaces, and generates syntactically ill-formed HTML if they are introduced. Other aspects of these cosmetic edits may further compound the problem. [[User:Hout|Hout]] ([[User talk:Hout|talk]]) 09:59, 22 September 2016 (UTC)
: Visibility of task descrption formulae restored by [[User:TobyK|TobyK]] Nov 7 2016
: (A couple of formulae remain coincidentally invisible in the preamble to the GAP contribution) [[User:Hout|Hout]] ([[User talk:Hout|talk]]) 15:21, 7 November 2016 (UTC)
::There is no space around the invisible formula in the GAP section. Also, it prints correctly on Wikipedia: [https://en.wikipedia.org/wiki/User:Kiwipidae/Test test]. I don't intend to circumvent a botched LaTeX implementation. [[User:Arbautjc|Arbautjc]] ([[User talk:Arbautjc|talk]]) 16:39, 7 November 2016 (UTC)
::: Helpful to readers, perhaps, to add a note that you have only managed to make those two formulae '''(k \mathrm{atan}(x)''' and '''\frac{5\pi}4)''' visible in Firefox ? (And perhaps give plain text equivalents ? Very understandable that you don't want to pay the price of someone else's Latex limitations, so I'm sure you won't want your readers to pay it either :-) [[User:Hout|Hout]] ([[User talk:Hout|talk]]) 17:05, 7 November 2016 (UTC)
::::Actually, I'm already paying it, since I am using Opera now. You are right, I can change the formula to text. [[User:Arbautjc|Arbautjc]] ([[User talk:Arbautjc|talk]]) 19:11, 7 November 2016 (UTC)
:::::: PS I don't know what your view is of the parallel issue in the Python contribution to https://rosettacode.org/wiki/Faulhaber%27s_formula [[User:Hout|Hout]] ([[User talk:Hout|talk]]) 15:57, 21 November 2016 (UTC)
::::: :-) Many thanks – one more page completely clear of that 'exheight' glitch now [[User:Hout|Hout]] ([[User talk:Hout|talk]]) 19:26, 7 November 2016 (UTC)
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