Page 201 - IM_FL_Geometry_Print Sample

rotation
A rotation is de ned 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 gure has rotational symmetry if there is a rotation that takes the gure onto itself. (We don't count rotations through angles such as and that leave every point on the gure where it is.)
scale factor
The factor by which every length in an original gure is increased or decreased when you make a scaled copy. For example, if you draw a copy of a gure in which every length is magni ed by 2, then you have a scaled copy with a scale factor of 2.
sector
The region inside a circle lying between two radii of the circle.
similar
One gure is similar to another if there is a sequence of rigid transformations and dilations that takes the rst gure onto the second.
sine
The sine of an acute angle in a right triangle is the ratio (quotient) of the length of the opposite leg to the length of the hypotenuse.
square
A quadrilateral with four right angles and four congruent sides.
symmetry
A gure has symmetry if there is a rigid transformation which takes it onto itself (not counting a transformation that leaves every point where it is).
tangent
The tangent of an acute angle in a right triangle is the ratio (quotient) of the length of the opposite leg to the length of the adjacent leg.
tangent
A tangent to a circle is a line that intersects the circle at exactly one point without cross the circle.
tessellation
An arrangment of gures that covers the entire plane without gaps or overlaps.
translation
A translation is de ned using a directed line segment. It takes a point to another point so that the directed line segment from the original point to the image is parallel to the given line segment and has the same length and direction.
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