Term | Definition |
Geometry | the study of points, lines, angles, surfaces, and solids. |
Point | a location in space |
line | a collection of points that extend forever in the same direction |
line segment | part of a line, 2 endpoints |
ray | a line that has a beginning point but no end |
angle | two rays with the same endpoint |
vertex | the point where two rays meet |
plane | a flat surface that extends forever in all directions |
parallel lines | lines that are always the same distance apart |
intersecting lines | lines that cross in the same plane |
perpendicular lines | intersecting lines that cross and form four right angles |
acute angle | less than 90 degress |
right angle | 90 degrees |
obtuse angle | greater than 90 but less than 180 degrees |
straight angle | 180 degrees |
reflex angle | between 180 and 360 degrees |
supplementary angles | 2 angles that measure 180 degrees |
complementary angles | 2 angles that measure 90 degress |
polygon | a closed plane figure with 3 or more sides |
triangle | 3 sides |
quadrilateral | 4 sides |
pentagon | 5 sides |
hexagon | 6 sides |
heptagon | 7 sides |
octagon | 8 sides |
nonagon | 9 sides |
decagon | 10 sides |
dodecagon | 12 sides |
Right Triangle | one 90 degree angle |
Obtuse Triangle | one angle more than 90 degrees |
Acute Triangle | all angles are less than 90 degrees |
Scalene Triangle | no sides equal and no equal angles |
Isosceles Triangle | 2 sides equaland 2 equal angles |
Equilateral Triangle | 3 sides equal and 3 angles that are 60 degrees each |
Square | 4 equal sides and 4 right angles |
Rectangle | 4 right angles and the opposite sides are equal |
Rhombus | 4 equal sides and the opposite angles are equal |
Parallelogram | 2 pairs of equal and parallel sides |
Trapezoid | one pair of parallel sides and one pair of sides that are not parallel |
sum of the measure of the interior angles of triangle | 180 degrees |
Perimeter | shortest distance around the outside of a polygon |
Perimeter Formula | add up all the sides |
Area | number of square units needed to cover a surface |
Altitude | height of a polygon |
Area of a Square | base x height |
Area of a Rectangle | base x height |
Area of a Parallelogram | base x height |
Area of a Triangle | 1/2 base x height |
Area of a Trapezoid | 1/2 x h x(base 1 + base 2) |