Physics Question? Help please?

Question

A pedestrian moves 4.4 km east and then 7.8 km north.
Find the magnitude of the resultant displacement vector. Answer in units of km

Part 2 of the question
What is the direction of the displacement vector (using the counter-clockwise angular direction to be positive, within the limits of -180° to +180°)? Answer in units of ° .

can you please explain how you got the answer, thanks best answer 10 points!

Answer 1

In our convention, east is to our right and west to our left. North is at top and south at the bottom. Hence if you put in the coordinates, the positive x direction is pointing to the east, and the positive y direction is pointing to the north. The displacement vector d = 4.4i + 7.8j.
|d| = sqrt(4.4^2 + 7.8^2) by Pythagorian's theorem
let the angle d makes with x-axis to be theta:
tan(theta) = 7.8/4.4, thus:
theta = tan^(-1) (7.8/4.4)