None. Parallel lines are lines that will never cross each other, no matter how long you make them. A triangle is a polygon that has three sides and...

Does a triangle have parallel lines?

A triangle is a geometric shape that always has three sides and three angles. Triangles have zero pairs of parallel lines.

How do you prove that a triangle is isosceles?

One way of proving that it is an isosceles triangle is by calculating the length of each side since two sides of equal lengths means that it is an isosceles triangle.