A triangle can never have any parallel lines because there must be three angles that add up to 180 degrees, which makes it impossible for the three sides to avoid intersecting. A parallel line can never intersect with another, and triangles must always have intersecting sides.
To test if two lines are parallel, try to draw a third line connecting the two and see if it forms a right angle. When drawing a third line connecting two sides of a triangle, it is never possible to form a right angle. Shapes that have parallel lines, such as parallelograms, form right angles with this new line drawn between the sides.