Please explain me to understand solution: A ship starts at point A and sails 5 km on a bearing of 135 degrees to point B.

[Laia]

Hello, can someone explain why do they subtract 78 from 270? I thought it needs to be subtracted from 360. I've attached the question and marking scheme. Also, there's another problem that I do not understand, it's also a bearing problem so please help me understand these.

This is the another question I need to understand.

 

[Dr.Peterson]

This is the another question I need to understand.

As in the other problem, please be specific: What do you not understand? Where do you need help?

 

[eipi45]

There is no mention of 78deg in your attachments, so not sure what your question is!

For the question attached, in order to find angle ABC, we only need to know the angle AB makes with North (255deg is already known and total will be 360deg)

The angle between AB and North is related to the angle between AB and North at the other end - it's 135deg there and the North lines make up two parallel lines with AB crossing them. Do you know the properties of a line crossing parallel lines? Corresponding/complementary angles? That is what all work on bearings hinges on.

Spoiler

So by corresonding angles AB makes 180-135=45 deg with North

Add that to 255deg to get 300deg

So ABC is 60deg