They are said to be perpendicular. Or, if you wanted an example of a pair of such lines, one example is a plus sign.
I hope the following is helpful to you.
http://en.wikipedia.org/wiki/Vertical_(angles)
The opposite angles formed by the intersection of two lines are called vertical angles. These angles are always congruent and share the same vertex.
these angles are called intersecting lines
vertical angles
Adjacent angles
They are equal opposite vertical angles and if the lines are perpendicular to each other then 90 degree angles are formed.
If the two lines form an X then each angle directly across from another is congruent or equal to that angle.
Vertical equal opposite angles are formed when lines intersect each other.
Vertical equal opposite angles are formed when lines intersect each other.
If I understand the question: Either pair of opposite angles formed by the intersection of 2 lines.
Perpendicular if they form right angles if not they form vertical opposite equal angles
They are angles formed when two straight lines intersect: they are on opposite sides of the point of intersection.
When two straight lines intersect they form 360 degees with opposite angles being equal.
Sponge Bob(:
Perpendicular Lines form right angles at their point of intersection
Perpendicular lines