###
point of concurrency for perpendicular bisectors

circumcenter

###
point of concurrency for angle bisectors

incenter

###
point of concurrency for medians

centriod

###
point of concurrency for altitudes

orthocenter

###
angle bisector

a ray that divides an angle into 2 congruent parts

###
median

a segment whose endpoints are a vertex of a triangle and the midpoint of the opposite side

###
altitude

a perpendicular segment from the vertex to the opposite side

###
concurrent lines

three or more lines that intersect at the same point

###
perpendicular bisector

a segment line ray or plane that is perpendicular to a segment at it's midpoint

###
quadrilateral

a four-sided figure

###
parallelogram

a quadrilateral with two pairs of opposite sides congruent

###
rectangle

a parallelogram with four right angles

###
rhombus

a parallelogram with four sides congruent

###
square

a parallelogram with four right angles and four sides congruent

###
kite

a quadrilateral with adjacent sides congruent and no opposite sids congruent

###
trapezoid

a quadrilateral with one pair of parallel sides

###
isosceles trapezoid

a trapezoid whose non-parallel sides are congruent

###
consecutive angles

angles that share a side

###
consecutive sides

sides that share a vertex and are next to each other

###
diagonal

a line connecting two nonconsecutive vertices of a polygon

###
base angles (of a trapezoid)

angles that share a base

###
midsegment

a segment connecting the midpoints of two sides

###
point of concurrency

the point at which three or more lines intersect

###
perpendicular bisector of a triangle

a line that cuts a triangle directly in half

###
negation

statement with the opposite truth value

###
conditional

an if... then statement

###
inverse

negates both parts of a conditional

###
contrapositive

negates and switches the parts of a conditional

###
equivalent statements

statements with the same truth value

###
indirect reasoning

reasoning in which all possibilities are considered and all but one are proved false

###
sss postulate

proves if triangles have three congruent sides, they are congruent

###
sas postulate

proves if two sides and the angle between them are congruent in a pair of triangles, the triangles are congruent

###
asa postulate

proves if two angles and the side they share are congruent in a pair of congruent triangles, the triangles are congruent

###
aas

proves if two angles and a non-included side are congruent in a pair of triangles, the triangles are congruent

###
CPCTC

corresponding parts of congruent triangles are congruent

###
isosceles triangle

a triangle with two congruent sides

###
corollary

a statement following a theorem

###
transversal

a line that intersects two coplanar lines

###
alternate interior angles

nonadjacent angles that lie on opposite sides of a transversal

###
same side (consecutive) interior angles

angles that lie on the same side of a transversal

###
corresponding angles

angles that lie on the same side of a transversal in corresponding positions

###
alternate exterior angles

angles that lie outside of the lines on the opposite sides of a transversal

###
same side exterior angles

angles that lie outside of the lines on the same side of a transversal

###
linear pair

supplementary, adjacent angles

###
vertical angles

angles that are made with intersecting opposite rays

###
equilateral (also equiangular)

all sides congruent of a triangle

###
equiangular (also equilateral)

all angles congruent of a triangle

###
regular polygon

a polygon that is both equiangular and equilateral

###
p

symbol for the hypothesis of a conditional

###
q

symbol for the conclusion of a conditional

###
biconditional

if then only if statement (both conditional and converse are true of a statement)

###
deductive reasoning

reasoning logically to reach a conclusion

###
law of detachment

if the first part of a conditional is true, the second part is true

###
law of syllogism

if p then q, if q then r, if p then r

###
reflexive property

a congruent to b, b congruent to a

###
transitive property

a congruent to b, b congruent to c ,then, a congruent to c.

###
complementary

angles whose measures add up to 90

###
supplementary

angles whose measures add up to 180

###
plane

a flat two dimensional surface

###
line

a series of points extending in different directions without ending

###
point

a location represented by a dot on a graph

###
space

the set of all points, 3D

###
skew lines

lines that are noncoplanar and never intersect

###
parallel lines

coplanar lines that never intersect

###
line

planes intersect in exactly one...

###
point

lines intersect at exactly one..

###
angle

two rays with the same endpoint

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