Direction of Displacement Vector [2D Kinematics]

[stickyriceyum]

Homework Statement

Question 1 [Correctly Solved]
A pedestrian moves 2.1km east and then 20km north. Find the magnitude of the resultant displacement vector. Answer in units of km.

Answer = 20.1km

Question 2
What is the direction of the displacement vector (using the counter-clockwise angular direction to be positive, within the limits of -180 degrees = 180 degrees)? Answer in units of degrees/

The Attempt at a Solution

[Theta] = (arctan) (Ay/Ax)
[Theta] = (arctan) 20km/2.1km = 1.466

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I'm probably using the wrong equation. :x
(using the counter-clockwise angular direction to be positive, within the limits of -180 degrees = 180 degrees) Also, I don't understand what that means. Will someone please explain?

 

[abelanger]

question #1: Draw it on a sheet of paper, make a Cartesian plane, use the upper y-axis as north, right x-axis as east. You ll remember something!
*hint* Pythagorean Theorem ;)

Question #2: now I am not sure if ill explain this right but! i think that this : "using the counter-clockwise angular direction to be positive, within the limits of -180 degrees = 180 degrees" means find the angle opposite to the 20km line (i think its the angle between the hypotenus and the 2.1km line)
Let's say it is ;)
now remember SOHCAHTOA and see if you can do it.

Got more questions, just PM me. Goodluck!