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# Geometry

### Vocabulary

TermDefinition
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
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)
Created by: ppearson