Vertically opposite angles are two angles formed by two intersecting lines that do not share an arm. A transversal is a line that intersects two or more other lines at distinct points. Complementary angles have a sum of 90 degrees, while supplementary angles have a sum of 180 degrees. Parallel lines in a plane do not intersect when extended indefinitely in either direction.

1. Lines and angles
adjacent angles

2. Vertically opposite angles.
• Two angles formed by two intersecting
lines having no common arm are called
vertically opposite angles.

3. Transversal
 A line which intersects two or more
lines in a plane at distinct points is
called a transversal.

4. Complementary angles.
 Whose sum is 90

5. Supplementary angles.
Whose sum is 180.

6. Parallel lines.
• Lines in a plane are parallel if they do not
intersect when produced indefinitely in
either directions.