Maths - it could happen to you.

Thursday, 19 May 2016

I have a very strange history with maths.  I did advanced maths at high school, and the hardest maths level at HSC level,  and I always walked out of the tests and exams feeling completely confident that I knew exactly what I was doing and I'd passed. But half the time I'd get the test or exam back and discover I'd got some ridiculously low score like 14%. It was very un-nerving.  By the time I reached the end of year 11 I'd lost so much confidence that it at least didn't surprise me when I failed the final exam and had to repeat the subject the next year. 

I was so un-nerved by this experience that when I was forced to do some maths units at uni half a decade later I panicked..  I was completely paranoid that I'd fail and get thrown out of my course. I worked so hard to avoid that outcome that I actually received university awards for both the maths and statistics units.  What the??  So I still don't know if I'm good at maths, or if I'm an idiot. Or maybe I'm average, and everyone else at uni that year were idiots.  Who knows.  It could have been that the uni subjects contained a lot more statistics and things like queuing theory which I really enjoyed for their more obvious real life applications (gambling and anywhere with queues), whilst the algebra and trigonometry at HSC perhaps seemed more abstract, and less applicable to real life..

So - what I'm trying to say here (in this long winded introduction), is that the last time I did trigonometry I had a spiked haircut (short on top, long at the back) and Australia had not yet celebrated its bicentennial.  In fact when I closed my answer booklet at the end of the HSC maths exam (2nd time around) I probably thought that my troubled relationship with Sines, Cosines, Quadratic Equations and the rest of the trigonometric palarva was over..

But here we are 30 years later, and my current woodworking project involves making a frame for a mirror.  A circular mirror. And the frame is made up of lots (35) bits of wood pointing outwards.  Like that sketch below

 

So to work out how to cut these peices of wood so they fit nicely (or nice-enoughly) together, I've had to pull some maths out of the dusty reaches of my brain and work out some angles.  Using Pi, tan, and arctan.  Thank goodness the internet has sprung up since I solved my last trig problem - not that it could solve the problem for me, but it could remind me of the tools I could use to do it. If you're interested,  I worked out the outside diameter and then the inside diameter.  Turning the inside into a percentage of the outside, I could work out how much length each piece would need to 'cut in' on either side.  What I really wanted was the angle to put my dropsaw onto though. So using my two values I used a tan equation (I had adjacent and opposite lengths).  From there it was a matter of using arctan to determine what the angle was. Therefore the angle to set my dropsaw was 90 minus the value I'd found.   Phew!

 

And did it work? Yeah - pretty much. It was a bit of a pain that I had about 7 different widths of wood - so I had to repeat the calculation each time - if I hadn't chucked out my scientific calculator all those years ago I would have used it so I could just plug in the lengths.  Of course calculating the angle down to two decimal points wasn't all that useful, as the drop saw only really had 1 degree settings, but I could at least eyeball an approximate setting.  It wasn't perfect, but it wasn't too bad.  I'm sure the imperfectness of my woodworking skills that I'll be using to complete this project will far outweigh any errors I've made in my calculations and cutting.  

2016summary
Christmassy Photos Friday, 30 December 2016
Noosa - Day 5 Thursday, 15 December 2016
Noosa - Day 4 Tuesday, 13 December 2016
Noosa - Day 3 Monday, 12 December 2016
Noosa - Day 2 Sunday, 11 December 2016
Noosa - Day 1 Sunday, 11 December 2016
Being Bothered Pays Off. Sunday, 11 December 2016
Swimming tour of Brisbane part 2 Sunday, 11 December 2016
Paver Project Wednesday, 23 November 2016
Swimming tour of Brisbane Wednesday, 23 November 2016
The end of an era Tuesday, 8 November 2016
Snowvember Tuesday, 8 November 2016
Tramp-a-bag Monday, 31 October 2016
Mt Wellington Monday, 31 October 2016
Online Only Challenge Monday, 31 October 2016
3 Capes Monday, 10 October 2016
Packing Regrets Wednesday, 5 October 2016
Fantasy Amazing Race Tuesday, 4 October 2016
Before and After then After that #37 Monday, 3 October 2016
Before and After #36 Zali's Room Take 2 Monday, 3 October 2016
That's DR McComb to you.. Friday, 26 August 2016
'Mrs', 'Miss', or 'Dammed feminist'? Sunday, 14 August 2016
Who is really paying for the bake sale? Friday, 12 August 2016
Running Sunday, 31 July 2016
The Kettering Incident and Why I am the Smartest in the Room Friday, 29 July 2016
Before and After Sneak Peak Tuesday, 26 July 2016
Vacuum Cleaner Update Tuesday, 26 July 2016
How not to go to the movies Tuesday, 12 July 2016
How Not to Sell Vacuum Cleaners Monday, 11 July 2016
Melbourne Mini Break Monday, 27 June 2016
60 Walks Challenge - Walk #35 Thursday, 23 June 2016
Treasure Chest Cake Thursday, 23 June 2016
Shark House! Saturday, 11 June 2016
Before and After #35 - CD Tower to Mirror Tuesday, 31 May 2016
Maths - it could happen to you. Thursday, 19 May 2016
Power Tools Tuesday, 17 May 2016
60 Walks Challenge - Walk #35 Friday, 22 April 2016
Sheffield Rail Trail & Derby Thursday, 21 April 2016
60 Walks Challenge - Walk #34 Wednesday, 20 April 2016
60 Walks Challenge - Walk #31 & #32 & #33 Wednesday, 20 April 2016
60 Walks Challenge - Walk #29 & #30 Tuesday, 19 April 2016
Creatures of Habit Thursday, 7 April 2016
Let me count the ways.. Wednesday, 30 March 2016
Canberra 2016 Friday, 25 March 2016
Un armed.. Wednesday, 16 March 2016
Full day of activities Sunday, 13 March 2016
Dumped Saturday, 12 March 2016
Double Tromble Friday, 11 March 2016
Million Dollar Lane Wednesday, 9 March 2016
2nd International MFSC Tuesday, 8 March 2016
Tip Run Tuesday, 8 March 2016
Blackberry Season Thursday, 3 March 2016
Packed Lunches Wednesday, 2 March 2016
so yeah.. Sunday, 28 February 2016
Cradle Mountain Run Curse Tuesday, 9 February 2016
Last Pictures Tuesday, 9 February 2016
All the kids Tuesday, 9 February 2016
Overland Track - Day 7 Monday, 25 January 2016
Overland Track - Day 6 Monday, 25 January 2016
Overland Track - Day 5 Sunday, 24 January 2016
Overland Track - Day 4 Wednesday, 20 January 2016
Overland Track - Day 3 Tuesday, 19 January 2016
Overland Track - Day 2 Tuesday, 19 January 2016
Overland Track - Day 1 Monday, 18 January 2016
Overland Track - Day 0 Sunday, 17 January 2016
Slow Progress Thursday, 14 January 2016
Pakning på, opp og stå, ut og gå Monday, 11 January 2016