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M1- vectors

https://imgur.com/a/0p09g

How they find the angle SAB (where 60 come from)?
at last where 180 come from (Highlighted)
Reply 1
Avatar for Shaanv
Shaanv
17
See if u can use my diagram and hints to work it out.

In mechanics i always draw loads of lines on my diagrams to try and work out angles. U gotta have some decent geometry skills to identify angles etc.



To find the angle i labelled as gamma use angles in a triangle.

Idk why i went with the greek alphabet just trying to be fancy😂
(edited 6 years ago)
Reply 2
Avatar for Qer
Qer
OP
16
Original post by Shaanv
See if u can use my diagram and hints to work it out.

In mechanics i always draw loads of lines on my diagrams to try and work out angles. U gotta have some decent geometry skills to identify angles etc.



To find the angle i labelled as gamma use angles in a triangle.

Idk why i went with the greek alphabet just trying to be fancy😂



o
so How to find what is alpha and beta

CAN YOU PLEASE EXPLAIN ME
(edited 6 years ago)
Capture.PNG164.9KB
Reply 3
Avatar for Shaanv
Shaanv
17
Original post by Qer
o
so How to find what is alpha and beta


I believe the way u find alpha is called co-interior angles.

Theres a nice demo on here to show what i mean.

http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/parallellinesrev1.shtml

Lmk if u need further help.
(edited 6 years ago)
Reply 4
Avatar for Shaanv
Shaanv
17
Original post by Qer
o
so How to find what is alpha and beta

CAN YOU PLEASE EXPLAIN ME


Also my diagram is wrong, just realised the alpha at B is not the same as the alpha at A.



Looking at it u only really need to find the angle labelled w.
Reply 5
Avatar for Qer
Qer
OP
16
Original post by Shaanv
Also my diagram is wrong, just realised the alpha at B is not the same as the alpha at A.



Looking at it u only really need to find the angle labelled w.


i AM STILL struggling. can you please explain me full method please
Reply 6
Avatar for Shaanv
Shaanv
17
Original post by Qer
i AM STILL struggling. can you please explain me full method please


Sure thing.

So u are trying to go from B to S.

You know the distance between B and S, now u need to find the bearing which the cadet should take to get from B to S.

120+theta+w=180 because 120+theta and w are co-interior angles.

They have worked out theta in the example so now u can work out w.

Remember bearings are measured from the north clockwise, so the bearing i want is the angle i have marked as phi, the circle with a line going through it.

So you know w and want to work out phi. What do u know about angles around a point?

Can u now figure out the bearing?

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