pre calc BEARING problems, multiple questions, please answer ASAP, I am very confused

Question

1)The bearing from A to B is 40°. Determine the bearing of A from B. 

2) If the beating from A to B is 120 degrees. Determine the bearing of A from B.

3) Describe in words what the bearing "N20 degrees W" means. You may wish to give directions or an alternative way to describe the location.

 

 

 

Answer 1

Hi Hannah:

 

   The way I read this problem, following the bearing "from A to B" takes you from Point A to Point B.  Following the bearing "from B to A" takes you from Point B back to Point A.  So, imagine going from A to B, and then wanting to go back to A.  What do you do?  At Point B, you turn around, which we commonly think of as "doing a 180;" in other words, turning 180^o.

 

   Thus, to get the bearing from B back to A, you just have to take your bearing from A to B and add 180^o.  So, 40 + 180 = 220^o for the first.  Then 120 + 180 = 300 degrees for the second.

 

   For the third, I agree with Kenneth, that this means 20 degrees west of north.  If you draw a standard set of x-y (Cartesian) axes, you can label the +x axis as east, then going around to north (+y axis), west (-x axis) and south (-y axis).  By this reckoning, 20 degrees west of north means veer 20 degrees to the west of due north, as Kenneth said.  

   In my experience, angles are conventionally measured from the +x axis counterclockwise (in other words, starting at die east and then swinging around counterclockwise.  By this reckoning, an angle 20 degrees west of due north would be 90 degrees (the angle from east to north) plus the additional 20 degrees past north, heading towards west, so 90 + 20 = 110 degrees

 

   But I would defer on the last question to those who are more experienced with compass directions.

Answer 2

1)The bearing from A to B is 40°. Determine the bearing of A from B.

 

These problems are fairly easy if you make a drawing!

Make a vertical line from point A upward to N (north).  From A, draw a segment ending in point B, 40 degrees away from the AN line (so that B is, in effect, in the first quadrant, i.e. above and to the right of A).

 

Find the angle from B back to A; it's 180+40 = 220^o--that's the bearing. (We're measuring angles in a clockwise manner, relative to North.)

 

3) Describe in words what the bearing "N20 degrees W" means. You may wish to give directions or an alternative way to describe the location.

It means 'basically, go due north, but veer away 20^o to the west. Net bearing is360-20 = 340^o

Answer 3

The bearing to a point is the angle measured in a clockwise direction from the North line.

N20ºW means the direction (not bearing) is 20º west of north.  If the compass has 0° (and 360°) pointing North and degrees are clockwise (that is, 90° is East), then the direction N20°W is the bearing 340°.

Airport runways have large numbers at each end (see an aerial view on the Internet) – for example, 17 and 35 that mean 170° and 350°.

Now: (1) going in the opposite bearing of 40° is 220°.  [note: your either add or subtract 180°]

And (2) the opposite bearing from 120° is 300°.

 

(note: bearings give directions (clockwise from the North line); they are not vectors and they have no indication of distance between points)