VOCABULARY central angle an angle that has the center of a circle as its vertex
chord a line segment that connects two points on a circle
corresponding angles two angles in the same position on different lines
endpoint a point that marks the end of a line segment or ray
equiangular equal angles
equilateral equal side length
image a shape or object that has been transformed
incscribe to draw one geometric figure inside another
intercepted arc an arc between the endpoints of two radii
interior angles inside angles
line an infinite set of points forming a straight path that continues in two directions
line of reflection the mirror line; the line across which a figure is flipped
line segment a part of a line bounded by two endpoints
line symmetry property that allows a figure to be folded along a line to create two congruent mirror images
parallelogram a quadrilateral with two sets of parallel and congruent sides
plane a flat surface that continues in all directions
point a position in space
quadrilateral a polygon with 4 sides
radius (pl. radii) a line segment from the center of a circle to any point on the circle
ray a part of a line that has one endpoint and continues in one direction
reflection a transformation in which a figure is flipped across a line to give a mirror image of the original figure
regular polygon a polygon whose sides are all the same length and whose angles are all the same measure
right triangle a triangle with one angle that measures 90°
rotational symmetry property that allows a figure to be rotated less than 360° and still look the same
scalene triangle a triangle with no sides equal
semi-circle an arc with a measure of 180 degrees
similar triangles that have the same shape but not necessarily the same size
supplementary angles two angles whose sum is 180°
transformation a change made to a shape or object
translation a transformation in which a figure is slid to a new location
transversals lines that intersect two or more lines to create angles
Triangle Inequality Theorem any side of a triangle must be shorter than the sum of the other two sides
vertex the point where two line segments, lines, or rays meet to form an angle
vertical angles congruent angles that are opposite from one another at the intersection of two lines