Apply the Pythagorean theorem to get the resultant velocity:
V =
Given values:
Vx = 57.8m/s
Vy = 5.6m/s
Plug in and solve for V:
V = 58.1m/s
EDIT: Let's get the direction of the resultant velocity as well.
This equation will give the angle of the velocity as measured off of the ground:
θ = tan⁻¹(Vy/Vx)
Again, the given values are:
Vx = 57.8m/s
Vy = 5.6m/s
Plug in the values and solve for the angle θ:
θ = tan⁻¹(5.6/57.8)
θ = 5.5°
The resultant velocity is oriented 5.5° off the ground.