A Bearing qn. (1 Viewer)

[Getteral09]

hey, could anyone work this bearing problem out?

Justin walks for 3.1 km due west then turns and walks for 2.7 km on a bearing of 205 degrees. How far is he from his starting point? Give your answer correct to 1 decimal point.

Thanks

 

[SoulSearcher]

Well, here's a diagram of the information, use the cosine rule to find out the length of the third side.

EDIT: angle is 115', not 105'.

 

[Riviet]

Wouldn't the bearing be taken from north or is it from his point of view (facing west)?

 

[SoulSearcher]

Well, if it's from the north, then my diagram still stands. If it is from his point of view, then the side of length 2.7km would be going upwards, with an angle between the sides of 155', I think.

 

[Riviet]

But shouldn't the angle in your diagram be 115 degrees (bearing taken from north)?

 

[SoulSearcher]

I need to develop addition skills

 

[bos1234]

could u plz help me how to solve this question?

thanks... wont the angle between them be 205 degrees?

 

[SoulSearcher]

Angle sum of a triangle cannot be above 180 degrees, for starters

If the bearing is taken as north, then by the cosine rule,

x² = 2.7²+3.1² - 2*2.7*3.1*cos115, solving for x, which is the third side length

 

[airie]

^No, as the bearing of 205 degrees is measured from the North line that points upwards in the clockwise direction

EDIT: I was replying to bos1234. SS is too quick

 

[bos1234]

thanks

airie and ss are u both doing ext 2 in year 12..
what do u normally average for ext 1 maths?

 

[dagwoman]

4.9km is my guess.

 

[Riviet]

4.9km is my guess.

I got that too.

 

[SoulSearcher]

airie and ss are u both doing ext 2 in year 12..
what do u normally average for ext 1 maths?

Umm, 90% in extension 1 maths, doing HSC exam this year. Doing extension 2 maths.