It is impossible for a triangle to have parallel lines since its three angles must sum up to 180 degrees, making it impossible for its three sides to not meet. A parallel line cannot meet with another parallel line, and triangles must always have sides that intersect.
To determine whether two lines are parallel, attempt to connect them with a third line and see whether it makes a right angle. When joining two sides of a triangle with a third line, it is never possible to produce a right angle. This new line drawn between the edges of parallelograms and other shapes with parallel lines creates right angles.
