Use the angle measuring tool to measure or validate the angle (in degrees) between
three points in a model.
On the 3D View contextual tabs set, on
the Mesh tab, in the Tools group, click the Measure angle icon.
On the Tools tab, in the
Tools group, click the Measure angle icon.
Under Point1, use Ctrl+Shift+left click to snap to points (for example,
named points, geometry points, geometry face centre, geometry edge centre, mesh
vertices and grid).