Chinahand Posted December 8, 2015 Share Posted December 8, 2015 (edited) @ paswt Yeah, but if someone doesn't fully understand the mathematics they are doing, they could easily make a logical error a bit like in my post #99 and end up with a mistake which is far less subtle than claiming a mouse weighs the same as a whale. As I said above I actually did this only a few weeks ago and the result could have been pretty serious if someone hadn't checked. Here's another one: I'm sure you'll agree ln(cos(x)) = ln(cos(x)) and if we double the first term we can say: 2 x ln(cos(x)) > ln(cos(x)) Now via logarithmic operation this means ln((cos(x))2) > ln(cos(x)) Now the natural logarithm is strictly increasing so this means (cos(x))2 > cos(x) Dividing through by cos(x) gives us cos(x) > 1 But it doesn't - cos(x) is always less than 1. Spot the deliberate error? Math's is sneaky ...paswt, do you get where the error is in post#99? Wrighty has given a strong hint, and I've tried to get people to think about it via what "s" actually is - the average of two different numbers. This is a thread on maths - these are thought provoking mathematical puzzles, "just saying" it is obvious post#99 is rubbish isn't the point - where/why is it rubbish. Only Wrighty has been willing to play along, the other responses have had quite an anit-mathematical flavour. Oh well. Edited December 8, 2015 by Chinahand Quote Link to comment Share on other sites More sharing options...
wrighty Posted December 8, 2015 Share Posted December 8, 2015 What if x=2i (for example - although I appreciate convention indicates x is a real number) - cos(x) is then greater than 1 and the inequality works. Again, you need to be aware of, and perhaps specify, the function's domain. Clearly no-one but me and China are interested in this sort of thing, but if they are - 2x is not necessarily greater than x, for example if x is negative (which it will be if it is the logarithm of a number less than 1) 1 Quote Link to comment Share on other sites More sharing options...
dilligaf Posted December 8, 2015 Share Posted December 8, 2015 I always thought that I was quite good at maths. Now I know that I wasn't. Quote Link to comment Share on other sites More sharing options...
the stinking enigma Posted December 8, 2015 Share Posted December 8, 2015 that was sums dilli. you were good at sums 1 Quote Link to comment Share on other sites More sharing options...
dilligaf Posted December 8, 2015 Share Posted December 8, 2015 that was sums dilli. you were good at sums Quote Link to comment Share on other sites More sharing options...
Lisenchuk Posted December 8, 2015 Share Posted December 8, 2015 I certainly can, can you see where the logic is incorrect? I would venture to suggest that you don't need 'logic' to know that a whale weighs more than a mouse . just saying You forgot to include the (GM) factor. = big mouse. Quote Link to comment Share on other sites More sharing options...
paswt Posted December 9, 2015 Share Posted December 9, 2015 that was sums dilli. you were good at sums Ah now I can contribute to a thread on 'sums' or arithmetic as we were told to call it at 'grammar school'. Good luck to those who find mathematics fascinating,I never did algebra and have managed to live my life,to my knowledge, without needing it. That said I did leave school at 15 and later got a 'post graduate diploma' and had to pass a 'statistics exam' and was advised by a clever mathematician how to pass the 'open book examination' which a number of folk with 'degrees' failed. China, I'm sorry I've been unable to 'play along' (we are all ignorant ,only in different subjects) ,and only posted as I was amused by your patronising attempted put down. Quote Link to comment Share on other sites More sharing options...
wrighty Posted December 9, 2015 Share Posted December 9, 2015 I never did algebra and have managed to live my life,to my knowledge, without needing it. This is one of the things about maths education that bugs me somewhat. Why is it that people are quite happy to admit to 'not doing maths', or 'never needing algebra' or whatever? You rarely find people who are proud of not being able to read. Quote Link to comment Share on other sites More sharing options...
the stinking enigma Posted December 9, 2015 Share Posted December 9, 2015 who is the better mathematician. you or jimmy white? Quote Link to comment Share on other sites More sharing options...
Mr. Sausages Posted December 9, 2015 Share Posted December 9, 2015 Eric Bristow is probably up there too. 1 Quote Link to comment Share on other sites More sharing options...
the stinking enigma Posted December 9, 2015 Share Posted December 9, 2015 people that can read also tend to be a little less condescending towards people that cant read than their mathematical counterparts, mainly because they are in the greater majority and thus less special Quote Link to comment Share on other sites More sharing options...
Chinahand Posted December 9, 2015 Share Posted December 9, 2015 Stinky - your immediate response to me putting up the maths problem was to question my practicality ... there's an irony in you now raising condescension, it cuts both ways. 1 Quote Link to comment Share on other sites More sharing options...
the stinking enigma Posted December 9, 2015 Share Posted December 9, 2015 if you read it again china you will see i was merely seeking your advice Quote Link to comment Share on other sites More sharing options...
the stinking enigma Posted December 9, 2015 Share Posted December 9, 2015 no i wasnt .. you are right .. im sorry Quote Link to comment Share on other sites More sharing options...
gettafa Posted December 10, 2015 Share Posted December 10, 2015 Can you change a wheel on a car or fit a dado rail? Can they fuck. (mind erm, neither can I) Quote Link to comment Share on other sites More sharing options...
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