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180º
Finish this sentence: "Angles
in a triangle add to . . ."
Acute Angle
An angle that measures
between 0 and 90 degrees
Adjacent Angles
What do we call angles that share a
common ray but no common interior
points
Angle Addition Postulate
If a point S lies in the interior of ∠PQR,
then ∠PQS + ∠SQR = ∠PQR.
Angle Bisector
cuts an angle into two equal
parts
Collinear
Points that lie on the same line
Complimentary angles
Two angles that add to 90º are
called
Conditional Statement
A statement that can be
written in if-then form.
Congruent
Figures that have the same size
and shape.
Conjecture
A statement you believe to be true
based on inductive reasoning
Converse
Exchange the hypothesis and
conclusion
Coplanar
points that lie on the same
plane
Counterexample
An example that proves a
statement false
Deductive reasoning
the process of using facts, properties, or
rules to justify reasoning or reach valid
conclusions
Inductive reasoning
The process of reasoning that a rule or
statement is true because specific cases
are true
Linear Pair
A pair of adjacent angles whose noncommon sides are opposite rays.
Midpoint
A point that divides the segment
into two congruent segments.
Obtuse Angle
An angle that measures more than 90
degrees but less than 180 degrees.
Postulates
Statements that are accepted
without proof
Ray
A part of a line, with one endpoint, that
continues without end in one direction.
Right angle
An angle of 90º is called a
Segment Addition Postulate
If B is between A and C, then
AB+BC=AC
Straight angle
An angle that measures 180º is
called a
Supplementary angles
Two angles that add to 180º
are called
Vertex
The corner (point) of an angle
where the two rays meet
Vertical Angles
A pair of opposite congruent angles
formed by intersecting lines