Given,
The diagram of the polygon with symmetry line is shown in question.
Required
The number of symmetry lines.
The axis or imaginary line that passes through the center of the shape or object and divides it into identical halves is called lines of symmetry.
From the diagram , it is clearly seen that 2 lines divided the shape into identical halves.
Hence, there are two lines of symmetry (line 1 and line 3).