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point

names a location

line

is perfectly straight and extends forever in both directions

plane

is a perfectly flat surface that extends forever in all directions

segment

is the part of a line between two points

ray

is part of a line that starts at one point and extends forever in one direction

angle

is formed by two rays with a common end-point called the vertex.

right angle

an angle that measures 90 degrees

acute angle

an angle that measures more than zero but less than 90 degrees

obtuse angle

an angle that measures more than 90 degrees, but less than 180 degrees

complementary angles

two angles whose measures add to 90 degrees

supplementary angles

two angles whose measures add up to 180 degrees

congruent figures

figures that have the same shape and same size

vertical angles

a pair of opposite congruent angles formed by intersecting lines

Triangle Sum Theorem

states that the measures of the angles in a triangle add up to 180 degrees

acute triangle

has 3 acute angles

right triangle

has one right angle

obtuse triangle

has one obtuse angle

equilateral triangle

has three congruent sides and angles

isosceles triangle

has at least two congruent sides and angles

scalene triangle

has NO congruent sides or angles

polygon

is a closed plane figure formed by three or more sides

regular polygon

a polygon with congruent sides and angles

trapezoid

a quadrilateral with exactly one pair of parallel sides

paralellogram

a quadrilateral that has 2 pairs of parallel sides

rectangle

a parallelogram with four right angles

rhombus

a parallelogram with all side congruent

square

a parallelogram with four right angles and four congruent sides