Adding vectors head to tail

Four displacements are laid head to tail, and the program draws them. Your job is to make it find their sum, the resultant: its two parts, its size and its direction.

The idea. Add all the $x$ parts, add all the $y$ parts, and then put the two totals back together:

Your tasks.

1. Inside the loop, add each dx to total_x and each dy to total_y.
2. Find the size of the resultant.
3. Find its direction in degrees, measured from the $+x$ axis.