Step-by-step explanation: The condition is not always true. As explained in the figure attached, In triangle AB, line MN is not parallel to the side BC but in triangle DEF, line PQ is parallel to the side EF. We can see that triangle AMN is not parallel to triangle ABC but triangle DPQ is similar to triangle DEF. Thus, for the triangles to be similar, the line should be parallel to the third side of the triangle with which the line is not intersecting.