**Angle** is a fraction of a circle. The **measure** of an angle is the size of the “turn” (rotation) that’s needed to get from the ray that forms one side of the angle to the ray that forms its other side.

**Supplementary angles** are angles which have measures that add to 180**Complementary angles** are angles which have measures that add to 90

**Adjacent angles** are angles that:

- share a vertex and one ray/side
- their interiors don’t overlap

**Non-adjacent angles** are angles that:

- may or may not share a vertex,
- but they don’t share a ray or even if they share a ray their interiors don’t overlap

## Transversal

*/transversal line - напречна линия/*

**Transversal** is a line that corsses at least two other lines.

### Transversal crossing parallel lines

Properties of transversal crossing parallel lines.

#### “Special” Congruent Angles

**Vertical angles**-- they share a vertex, but lie on the opposite sides of both the parallel lines and the transversal. **Corresponding angles**-- are matching angles that lie, one on each parallel line, on the same side of the parallel lines and the same side of the transversal. **Alternate interior angles**-- are angles that lie, one on each line, on opposite sides of the parallel lines and opposite sides of the transversal, inside of the parallel lines. **Alternate exterior angles**-- are angles that lie, one on each line, on opposite sides of the parallel lines and opposite sides of the transversal, outside of the parallel lines.

#### “Special” Supplementary Angles

**Consecutive interior angles**-- are angles that lie, one on each parallel line, on opposite sides of the parallel lines, but on the same side of the transversal. **Adjacent angles**-- are angles with the same vertex that lie on opposite sides of the parallel line, but on the same side of the transversal.

### N-gons

The sum of angles in an n-gon is

**Polygon Exterior Angle Sum Theorem**: If a polygon is a convex polygon, then the sum of its exterior angles (one at each vertex) is equal to 360 degrees.