h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hi Justin,

I've now amended A850691, using your suggestions from the Sub-editors' message board. Could you take a look and let me know if you think it's OK now? I think I've fixed the style, but the maths still makes my brain hurt!

In the introduction, 3rd para: 'the six being the three sides...' - should really be 'the three side lengths...', as that's all we can hope to know about the sides...

Ditto for the 'The Law of Sines' para, case b.

Introduction, last para: A footnote (or explaination) to the effect that 'congruent' means 'the same'?

Notation section: colinear = not all lying on the same (straight) line.

May also be worth mentioning that we can assume angles ? and ? are not 90° - if either of them is, we can re-label the points to move the right-angle to ?.

One or two things from the perspective of someone who's typeset a couple of mathematical papers in the last year: it is conventinal to have all the variable names (the A's, B's, C's, a's, b's, c's, ?'s, ?'s and ?'s) in italics. This includes the x's and y's in (eg) 'xy-coordinate place' and 'x-axis'.

Law of Sines: I would suggest brackets around the 'sin ?' (and ? & ?) in the first version of the expression - for consistency, if not clarity.

I would hyphenate coordinate, to co-ordinate.

'ratio of the side opposite to the hypotenuse' - I would change to something like 'ratio of [the length of the side opposite the angle] to [the length of the hypotenuse]', with an explaination to the effect that the hypotenuse is the side opposite the 90° angle. A bit wordy I know, but I think it's clearer.

Para beginning 'In triangle ACD' - it may be worth mentioning the if ?90°, the angle interior to triangle ACD at point A will be an angle ?', such that ?+?'=180°.
Then sin(?')=sin (180°-?)...

Final para - 'Substituing' - missing t
For clarity, I would write the equality as 'a*sin ? = CD = b*sin ?' (in bold, to give equal ephasis as the previous results).

The Law of Cosines:
Proof, second para: segment AC (side B) - should be lower-case b

QED should not have '.'s in it...

Other than that, great! It would *definitely* benefit from some diagrams though. Not sure what the proceedure is, but I'd be willing to do them.

J

Thanks, Justin.

There's obviously still plenty to do, and to be frank I think it's going to be simpler if I take you up on your offer to take over this entry. I'll post to the Subs list and see if that can be done.

It's with me now...

for rescuing me from it!

Hey Ormy!

Just after your opinion really - the diagrams are in - can you at least follow what's going on now, even if you don't really understand why?



J

The diagrams certainly help!

I haven't got time to read through the entry properly now as I'm in a public library where I'm only allowed 15 minutes online, but I'll have another look on Friday when I get home. Having a quick look at it now, I did just notice a typo at the end of the first paragraph under 'The Law of Cosines' - 'remainer' for 'remainder'.

I've now had another look, and although I don't claim to understand everything in the entry, the diagrams make it much easier to get some sort of handle on what's going on. Well done - you've done a far better job on the entry than I could have done!

Cheers mate!

I think it's the sort of thing that you *can't* understand properly without diagrams. Luckily, I've been well taught - I can picture the diagrams in my head. But for someone who has never done much/any trigonometry before, they need to be there in the flesh, as it were.