How many unfolded corners are formed when two straight lines intersect?

An extended angle is an angle whose sides form a straight line. The degree measure of the flattened angle is 180 °. As a consequence of this definition, we can assume that a non-deployed angle is an angle whose degree measure is different from 180 ° (more or less).
When two straight lines intersect, four non-deployed angles are formed, their sum is 360 °. Let’s designate these angles clockwise ∠1, ∠2, ∠3 and ∠4. The pairs of angles ∠1 and ∠3, ∠2 and ∠4 are equal, since they are vertical angles. Pairs of angles ∠1 and ∠2, ∠2 and ∠3, ∠3 and ∠4, ∠1 and ∠4 are adjacent and add up to 180 °.