Sweet! That wasn't very difficult, was it?
Given a vector's magnitude and its angle with the x-axis, we know how to calculate its x- and its y-components. How about the reverse? Given the components, can we calculate the magnitude and angle?

Yes! If $$\vec{A} = A_x \hat{i} + A_y \hat{j}$$, then, the magnitude is just $$\sqrt{A_x^2 + A_y^2}$$. The angle is calculated by taking the inverse tan of $$\frac{A_y}{A_x}$$