#1
Alright, I've started doing some preliminarily work for A2. This also means Mechanics.

It's not so bad so far, I'm just iffy on a few things so far on my work on vectors and thought to bring it here.

8. The vector a is in the plane Oxy, where Ox, Oy are the coordinate axis, and makes an angle 30 degrees with Ox, as in the above diagram (I'm too lazy to draw it out). Find the components of a long Ox and Oy when a equals;

There's four parts of this question if someone could do one of them (when a equals 6) I could try doing the rest from there.

Even easier one but for some reason I cannot get the direction at all. I keep getting the same answer which is wrong.

In a regatta a yacht sails x km due east from a marker O then y km due north to a buoy B. Calculate the magnitude and direction of the displacement vector OB> when

b. x=5, y=8
#3
Both questions are just Pythagoras dressed up with stupid wording.
#4
Quote by soulflyV
Lies! It IS another maths thread

Edit: Don't forget about bearings, that north is 0 degrees, and not 90. That used to mess me up all the time.

That might help some other stuff I was iffy on actually, cheers.

0 to 360 in a clockwise then?
#5
Quote by Craigo
8. The vector a is in the plane Oxy, where Ox, Oy are the coordinate axis, and makes an angle 30 degrees with Ox, as in the above diagram (I'm too lazy to draw it out). Find the components of a long Ox and Oy when a equals 6
a(Ox) = 6cos30, a(Oy) = 6sin30 I think but I haven't done this sort of stuff in a while.
#6
Quote by smb
Both questions are just Pythagoras dressed up with stupid wording.

Question eight has only two figures so I can't use Pythagoras just yet.

The other one I'm after the angle. The pythag part of that is easy, I just keep getting the wrong angle.
#7
Quote by Craigo
In a regatta a yacht sails x km due east from a marker O then y km due north to a buoy B. Calculate the magnitude and direction of the displacement vector OB> when

b. x=5, y=8
The angle from the x axis is sin^(-1) [sqrt(5^2+8^2) / 8] and the magnitude is sqrt(5^2+8^2)

again, I could be wrong, my maths is a bit rusty
#9
In question 8 use simple sin and cos. It's basically a right-angled triangle where the hypotenuse is 6cm long. Then get the base and height and put them into vector form.
#10
Quote by smb
a(Ox) = 6cos30, a(Oy) = 6sin30 I think but I haven't done this sort of stuff in a while.

Damn, that's all it is?

And yeah, that's actually correct. Cheers for that.

I'm working from a poor book with no actual help so there may be a few of these threads popping up.
#12
Quote by smb
The angle from the x axis is sin^(-1) [sqrt(5^2+8^2) / 8] and the magnitude is sqrt(5^2+8^2)

again, I could be wrong, my maths is a bit rusty

After re-wording I'm getting a lot of Math errors on the calculator. Mind re-writing that?
#14
Forget the first bit - I was doing it a stupid way. It's just inverse tan (8/5)
#16
Quote by smb
Forget the first bit - I was doing it a stupid way. It's just inverse tan (8/5)

Already tried. It's wrong.

Wait, crap! After doing that in about four different ways, getting the same answer, turns out I was reading the wrong answer. I had it correct the first million times...
#19
typical...

The textbooks we had when I was taking M1 were all new first editions and full of errors - loads of the answers were wrong.
#20
Quote by Craigo
Dyslexic


Excuses

Quote by smb
typical...

The textbooks we had when I was taking M1 were all new first editions and full of errors - loads of the answers were wrong.


The textbooks we have are third edition and still have loads of incorrect answers.

The books were written by mathematicians, but I can't see how they could let them go into print (for the third time mind you) with so many maths-related fuckups.
#21
Quote by soulflyV
The textbooks we have are third edition and still have loads of incorrect answers.

The books were written by mathematicians, but I can't see how they could let them go into print (for the third time mind you) with so many maths-related fuckups.
Well I think usually the questions are written by the book writer's students. Certainly students do the proof-reading (at a ****ty rate of pay)

I want to write a maths textbook myself some day - I'm planning on doing a masters in maths education once I finish my current degree.
#22
Quote by soulflyV
Excuses


The textbooks we have are third edition and still have loads of incorrect answers.

The books were written by mathematicians, but I can't see how they could let them go into print (for the third time mind you) with so many maths-related fuckups.

Yeah, the publisher I'm using is quite reknowned for it and it's bloody annoying.

And I was tempted to add in to my post 'inb4Dyslexia'snotanexcuseforstupidity'

I don't care, I joke about it and how miraculous it was I got an A in English Language at GCSE
#24
Quote by smb
Well I think usually the questions are written by the book writer's students. Certainly students do the proof-reading (at a ****ty rate of pay)

I want to write a maths textbook myself some day - I'm planning on doing a masters in maths education once I finish my current degree.

Awesome.

What's your educational history anyway? You always appear to be an patronising sod around the forums on academic matters
#25
Quote by Craigo
Awesome.

What's your educational history anyway? You always appear to be an patronising sod around the forums on academic matters
I've got A-levels in maths, further maths, physics, chemistry and religious studies. I'm doing my degree in physics with photonics and nanotech. I took most of last year out for health reasons so I'm re-doing my second year this year.

I don't mean to patronise but I can't help being very opinionated
#28
Quote by smb
I've got A-levels in maths, further maths, physics, chemistry and religious studies. I'm doing my degree in physics with photonics and nanotech. I took most of last year out for health reasons so I'm re-doing my second year this year.

I don't mean to patronise but I can't help being very opinionated

Psst. Arrogance and being egotistical are virtues, regardless of wingey opinions anyone else may give.
#29
Yeah exactly. If you don't have confidence in your opinions, you're probably wrong.