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re>ection
A reSection is deRned using a line. It takes a point to another point that is the same distance from the given line, is on the other side of the given line, and so that the segment from the original point to the image is perpendicular to the given line.
re>ection symmetry
A Rgure has reSection symmetry if there is a reSection that takes the Rgure to itself.
regular polygon
A polygon where all of the sides are congruent and all the angles are congruent.
rhombus
A quadrilateral with four congruent sides.
right angle
When you divide a straight angle into two congruent angles, each of the two angles is a right angle. For example, the four corners of a rectangle are right angles.
right prism
A right prism is one whose sides are perpendicular to its base.
rigid transformation
A rigid transformation is a translation, rotation, or reSection. We sometimes also use the term to refer to a sequence of these.
rotation
A rotation is deRned using a center and a directed angle. It takes a point to another point on the circle through the original point with the given center. The two radii to the original point and the image make the given angle.
rotational symmetry
A Rgure has rotational symmetry if there is a rotation that takes the Rgure onto itself. (We don't count rotations through angles such as and that leave every point on the Rgure where it is.)
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