###
straight angle

an angle whose measure is exactly 180 degrees

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right angle

an angle whose measure is exactly 90 degrees (we place a "block" at the vertex of the angle)

###
complementary

the sum of two angles is 90 degrees

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supplementary

the sum of two angles is 180 degrees

###
vertical angles

angles that are across from each other in an "x" pattern (equal to each other in measure)

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perpendicular lines

2 lines that intersect at a right angle

###
corresponding angles

angles that are in the same place in the top "x" as in the bottom "x"

###
congruent

when two angles are the same size, but we don't care about the angle measure

###
alternate interior angles

angles that are on the opposite sides of the line "t" and are inside the parallel lines

###
alternate exterior angles

angles that are outside of the parallel lines and are on opposite sides of line "t"

###
acute triangle

a triangle that has 3 acute angles

###
right triangle

a triangle that has one right angle

###
obtuse triangle

a triangle that has one obtuse angle

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equilateral triangle

a triangle that has 3 sides of equal length

###
isosceles triangle

a triangle that has 2 or more sides with the same length

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scalene triangle

a triangle that has no sides of the same length

###
quadrilateral

a closed figure with four sides that are line segments

###
trapezoid

a quadrilateral with exactly one pair of parallel sides

###
parallelogram

a quadrilateral with two pairs of parallel sides

###
rhombus

a parallelogram with 4 sides of equal length

###
rectangle

a parallelogram with 4 right angles

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square

a parallelogram with 4 sides of equal length and 4 right angles

###
diagonal

a segment that joins two vertices of a quadrilateral, but is not a side

###
polygon

a closed figure that's made up of 3 or more line segments that intersect only at their endpoints

###
regular polygon

a polygon with all sides equal in length and all angles equal in measure

###
sum of interior angles

(n-2) * 180

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measure of each interior angle

(n-2) * 180/n

###
Side-Side-Side (SSS)

If 3 sides of 1 triangle are congruent to 3 sides of another triangle, then the triangles are congruent

###
Side-Angle-Side (SAS)

If 2 sides and the angle between them (known as the "included angle") are congruent to 2 sides and the angle between them in another triangle, then the triangles are congruent

###
Angle-Side-Angle (ASA)

If 2 angles and the side between them (known as the "included side") in 1 triangle are congruent to 2 angles and the side between them in another triangle, then the triangles are congruent

###
reflection

a transformation that creates a mirror image of a figure

###
line of reflection

a line where the figure is reflected

###
transformation

a geometrical operation that change a figure into another figure

###
line symmetry

1 half of the figure is a mirror image of the other half folded over this line

###
image

the new figure created after a figure is transformed

###
translation

a transformation that slides a figure

###
coordinate notation

describes the transformation in terms of changes to the coordinates of the points in the figure

###
rotation

a transformation that turns each point of a figure the same number of degrees around a common point

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angle of rotation

the angle through which a figure is rotated

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center of rotation

the common point of the rotation's center

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similar polygons

polygons that have the same shape, but are not necessarily the same size

###
scale factor

the ratio of corresponding sides of 2 polygons

###
dilation

a transformation that stretches or shrinks a figure

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