Relationship between straight line ep and straight line fn
Vertical or orthogonal. If a straight line EP intersects with another straight line FN vertically, and their included angle at the intersection point P is a right angle (i.e. EP⊥FN, ∠ EPF = 90), then the two straight lines are perpendicular to each other. In mathematics, we call these two straight lines perpendicular or orthogonal to each other.