Final answer:
In mathematics, arrowheads are used at either end of a line to indicate that it extends indefinitely in both directions, representing an infinite one-dimensional path.
Step-by-step explanation:
To indicate that a line continues indefinitely in both directions in mathematical diagrams, arrowheads are drawn at either end of the line. This visual representation helps to convey that the line extends infinitely in both the negative and positive directions along a one-dimensional path.
In contrast, when a line segment, which has a definite start and end point, is depicted, no arrowheads are used, and sometimes the endpoints are denoted with dots or other marks. However, when illustrating concepts like electric field lines in physics, similar conventions may apply where lines originating from positive charges or extending to negative charges demonstrate the directionality and continuity of the field.
Moreover, in art, a line can be a dot or series of dots connected to form a continuous mark, which may vary in thickness, color, and shape. While lines in art can also be implied lines, where the viewer's perception completes the line, in mathematics and physics, the use of arrowheads is a clear indicator of infinite extension.