A million years ago, an alien species built a vertical tower on a horizontal plane.

A million years ago, an alien species built a vertical tower on a horizontal plane. When they returned they discovered that the ground had tilted so that measurements of 3 points on the ground gave coordinates of (0, 0, 0), (3, 2, 0), and (0, 1, 1). By what angle does the tower now deviate from the vertical?