What type of line makes use of rounded angles?

The type of line that makes use of rounded angles is a curved line. Curved lines bend to perform one or more turns between their end points.

Art uses curved lines to express fluidity. The frequency of the curving action in a piece's lines can communicate its intensity in movement, which can be seen in paintings, sculptures and sketches. Less curve in art typically creates a calmer effect, such as the shallow curves in the human form or the movement displayed by water. Artwork that uses deeper curves creates a crowding of its space. This commonly suggests turbulence, chaos or violence.