What are angles opposite one another at the intersection of two lines?

Answer 1

They are said to be perpendicular. Or, if you wanted an example of a pair of such lines, one example is a plus sign.

Answer 2

I hope the following is helpful to you.

http://en.wikipedia.org/wiki/Vertical_(angles)

Answer 3

The opposite angles formed by the intersection of two lines are called vertical angles. These angles are always congruent and share the same vertex.

Answer 4

these angles are called intersecting lines

Answer 5

vertical angles