"R" is the distance from the origin to the point.
R = √(-3² + 7²)
R = √(9 + 49)
R = √(58)
R = 7.62
tangent (Θ) = 7 / -3
Θ = arctan (7 / -3)
Θ = 113.2° counterclockwise from the x-axis
