A figure has line symmetry if there is a line about which the figure may be folded so that the two parts of the figure will coincide with each other. The imaginary line or axis along which you can fold a figure to obtain the symmetrical halves is called the line of symmetry. It is also termed the axis of symmetry. The line symmetry is also called a mirror line because it presents two reflections of an image that coincide.
Hence, a scalene triangle has all sides unequal so it has no line of symmetry.
