Maths question (core2)

[TheCenturion]

Here is the question

for A) it's easy. Just use the cosine rule

For part B) I drew a triangle LST and worked out the size of angle T. For the sake of simplicity, let's say it's 52'. But then how do you work out the bearing of S from T??? The markscheme for the paper says

285 + angle T

where does the 285 come from?

The radians bit is easy, it's 2 radians.

Then, the overall angle is 114.6'
But then the markscheme just says that the bearing can be anywhere between 293' and 294'

 

[jackthezipper]

Can't be bothered/remeber how to work it out.

285 though is L's bearing from T.

So 285 is T clockwise to L. Then your adding the angle of the corner (of the triangle) LTS.

 

[Kenai]

Dunno about the first part off the top of my head but your last question is very simple.

It started at a bearing of 48', so 'subtract' 114.6 if you see what I mean, but because you're working with angles rather than finish up with -66.6 you end up at 66.6' past 360 travelling anticlockwise, leaving you at a bearing of 293.4. Not the best explanation in the world (in fact it's pretty awful) but hopefully you see what I mean.

North / Up is always 0 with bearings IIRC.

The first part is probably similarly easy but i'm too drunk to put thought into it and the bottom question just jumped out at me

 

[skippy2421]

Can't be bothered/remeber how to work it out.

285 though is L's bearing from T.

So 285 is T clockwise to L. Then your adding the angle of the corner (of the triangle) LTS.

Pretty much it.

 

[mistercrabb]

I didn't know why I couldn't understand this at all.
Just realised there's an image that isn't loading in the OP

 

[skippy2421]

If you're still struggling to get the 285 draw a line dead up from T then think about angles and parallel lines.

 

[TheCenturion]

Hi guys, thanks for the replies, but I just don't understand how to get the bearings

 

[Kenai]

I assume you've been taught about and know what a bearing is?

 

[TheCenturion]

I assume you've been taught about and know what a bearing is?

I assumed that too

 

[WingZero30]

Lol I thought the question was related to calculations done by core 2 duo or core 2 quad cpu .

 

[Kenai]

Right, well i'll try and explain the part I did earlier with visual assistance this time.

I've added in there dotted lines where bearings of 90, 180, 270 and 0 would be. I've also marked out the starting bearing of 48.

You've previously calculated that figure of 114.6.

All you need to calculate your new bearing is to follow your 114.6 anti clockwise from your starting bearing of 48, which leaves you at 293.4.

It's essentially nothing more than subtraction but when you go below 0, you don't go to negative numbers, you go to 360 again because you're dealing with angles in a circle essentially.

If you can grasp this, then the explanation someone else provided for your other query should make sense and sort you out

 

[TheCenturion]

Oh okay, I see! Thanks very much for that explanation

I'll try and see if I can understand the first question now

 

[TheCenturion]

Okay, I'm still very confused:

Am I right in thinking that the angle I have marked as x is the bearing of S from T?

EDIT: just realised where I've gone wrong

EDIT2:

Still not sure how to get the 285.

 

[Kenai]

Yes you've marked out x as S from T, though you need L from T.

I'm not sure what the rule is called but you can find this angle of 75 using it, which then leaves you with 285 as your bearing of L from T. You need to temporarily forget about your triangle LST to get that initial bearing of 285.

You should be able to figure the rest out from there.

 

[TheCenturion]

Oh yes, corresponding angles on parallel lines are the same.

That makes sense now, I was missing the vital part about corresponding angles, thanks for your help

 

[Kenai]

Yeah that'll be the one

 

[TheCenturion]

I so badly want to get 90% in core 2...