Measurements of curvilineal angles

The angle between curves is in most cases dened as the angle between their tangents at the point of intersection. From an heuristic point of view this is unsatisfactory. For instance the angle between a circle and a tangent gets a measure 0 in this way. Yet we see a space between the two quite dierent from the space between two coinciding half-lines. The essential part of the paper concerns the denition of a non-trivial measure for the angle between tangent curves.