polygons

complementary angles

2 angles that add up to 90°

supplementary angles

2 angles that add up to 180°

a line that intersects 2 or more lines

transversal

angles that are formed at the intersection of 2 lines

opposite angles

opposite angles are

equal

sum of all angles around a point

360°

lines that never cross

parallel

lines that cross at a 90° angle

perpendicular

an angle inside a polygon

interior

an angle between the side of a polygon and the line extended from the next side is called

exterior

triangle

polygon with 3 straight lines and 3 angles

equilateral - all sides congruent

isosceles - 2 sides congruent

scalene - no sides are congruent

acute - all angles less than 90°

obtuse - one larger than 90° angle

right - one 90° angle

opposite sides are parallel & equal

parallelogram

angles are all 90°

rectangle

all sides are equal

rhombus

all angles are 90°

square

one set of parallel lines

trapezoid

kite

all angles less than 180°

convex quadrilateral

1 angle is greater than 180°

concave quadrilateral

triangle

square

pentagon

hexagon

heptagon

octagon

nonagon

decagon

diagonals

lines connecting vertices that are not next to each other