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straight angle

an angle whose measure is exactly 180 degrees

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

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)

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

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

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

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

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

angle of rotation

the angle through which a figure is rotated

center of rotation

the common point of the rotation's center

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