Using Vectors to Find Displacement and Angle

[sb13]

Homework Statement

A person walks in the following pattern: 4.1 km north, then 2.0 km west, and finally 2.5 km south.

Homework Equations

(a) How far (in km) and (b) at what angle (measured counterclockwise from east) would a bird fly in a straight line from the same starting point to the same final point?

The Attempt at a Solution

I know that I need to create the triangles for 4.1, 2.0, and 2.5, and use basic trigonometry (sine and cosine) to find the values of each of their x and y components, but I am not sure which reference angles to use 30 degrees, 60 degrees, 45 degrees? How am I supposed to tell? I know where to go from there, you add up all of the x components, and then all of the y components, and then create your final triangle and determine the displacement value using the Pythagorean Theorem. Then you determine the angle by using the inverse of tangent.
I just need help with determining the angles for those three triangles.

 

[ehild]

Hi sb13,

Make a drawing. Everything will be simple.

ehild

 

[sb13]

Thank you. I figured it out.