Question

The components of vector a⃗ are ax = + 3.90 and ay = -4.00. What is the angle measured counterclockwise from the +x-axis to vector a⃗ ?

Answer 1

The angle is the arctangent of the ratio of ay to ax. Since ay is negative and ax is positive, it is a 4th-quadrant angle.

... arctan(ay/ax) = arctan(-4.00/3.90) ≈ 314.27°

... about 5.48513 radians