Try using angles in radians. Most math libraries implement all trigonometry using radians. Part one rotates the vector such that it points from the origin into the direction of the end point. Part two then adjusts the lenght such that it exactly indicates the end point.

Greetz,

Illco

is this a polar coordinate way to solve the problem?
i thought initially that you could use the dot product.

(i guess that's why i'm sticking with 2D)