Basic Polygons and Some Angles

Congruent angle family

Angle 1 = Angle 2, (corresponding, vertical, alternate interior, and alternate exterior angles)

Supplementary angle family

Angle 1 = Angle 2 = 180 degrees, (linear pairs, same

Linear pair

A pair of adjacent angles that form a straight line and add up to 180 degrees.

Same-side interior angles

Two interior angles on the same side of a transversal line that are supplementary.

Same-side exterior angles

Two exterior angles on the same side of a transversal line that are supplementary.

Disproving an "All" statement

A logical rule stating that to disprove "All A are B", you only need to find a single counterexample where an A is not a B.

Polygon Interior Angle Sum Theorem

The formula used to find the total sum of all interior angles in any polygon: (n

Individual interior angle formula

The formula used to find a single interior angle of a regular polygon: [(n

Polygon

A closed geometric figure with all straight sides.

Triangle classification by angles

Triangles split into right (1 right angle), acute (3 acute angles), or obtuse (1 obtuse angle).

Triangle classification by sides

Triangles split into equilateral (all sides equal), isosceles (2 sides equal), or scalene (all 3 sides different).

Quadrilateral

A closed polygon with exactly 4 sides.

Parallelogram

A quadrilateral featuring 2 pairs of parallel sides.

Trapezoid

A quadrilateral featuring exactly 1 pair of parallel sides.

Rectangle

A parallelogram featuring 2 pairs of parallel sides and 4 right angles.

Rhombus

A parallelogram featuring 2 pairs of parallel sides and 4 congruent (equal) sides.

Rhombi

The correct plural form of the word rhombus.

Square

A highly specific parallelogram featuring 2 pairs of parallel sides, 4 right angles, and 4 congruent sides.

Pentagon

A polygon featuring exactly 5 sides.

Hexagon

A polygon featuring exactly 6 sides.

Octagon

A polygon featuring exactly 7 or 8 sides (specifically 8 sides).