Chapter 9 Properties of Transformations Warren Luo Matthew Yom

9.1 Translate Figures and Use Vectors  Transformations move or change a figure in some way to produce and image.  Image: A new figure that is produced by a transformation.  Preimage: The original figure of an image.  In previous chapters, you learned that after transforming a figure, you add prime signs. For example translating ABCD would result into A’B’C’D’

9.1 Translate Figures and Use Vectors Continued  Isometry: A transformation that preserves length and angle measure.  Theorem 9.1: Translation Theorem: A translation is an isometry.

Try This! Rectangle HLZT has points H(-1, 2) L(1, 2) Z(-1, -2) T(1, -2) is translated with (x, y)→(x+2, y-3), find its new points. H’(2, -1) L’(3, -1) Z’(1, -5) T’(3, -5)

9.1 Translate Figures and Use Vectors Continued  Vector: A quantity that has both magnitude and direction. It is represented in a coordinate plane by and arrow drawn from one point to another.  The initial point, or starting point is A. The terminal point or ending point is B The component form of a vector combines the horizontal and vertical components. So, the component form of vector AB is.

Try This!  Name the vector and write its component form. Vector AB

9.2 Use Properties of Matrices MMMMatrix: A rectangular arrangement of numbers in rows and columns. EEEElement: Each number in a matrix. DDDDimensions of a Matrix: The number of rows and columns in a matrix. TTTThis is a matrix:

9.2 Use Properties of Matrices Continued WWWWhen you add or subtract matrices, add or subtract corresponding elements. FFFFor example: HHHHowever, when you multiply matrices the number of columns in your first matrix must match the number of rows in the second one. So when you multiply, you multiply rows by columns, then add your results to get your new elements. For example: (5x0)+(3x1) (5x4)+(3x5) (0x0)+(1x1) (0x4)+(1x5) 1 5

Try This! Multiply Multiply

9.3 Perform Reflections  Reflection: A transformation that uses a line like a mirror to reflect an image.  Line of Reflection: The mirror line in a reflection.  Coordinate rules for Reflections If (a, b) is reflected in the x-axis, its image is the point (a, -b). If (a, b) is reflected in the y-axis, its image is the point (-a, b). If (a, b) is reflected in the line y=x, its image is the point (b, a). If (a, b) is reflected in the line y=-x, its image is the point (-b, -a).

9.3 Perform Reflections Reflection: A reflection is an isometry. Reflection Matricies Reflection Matricies 1 0 Reflection in the x-axis Reflection in the y-axis

Try This!  Rectangle CDEF has points C(-4, 5) D(-2, 5) E(-4,1) F(-2, 1) and reflect it over the y axis.  C’(4, 5) D’(2, 5) E’(4, 1) F’(2, 1)

9.4 Perform Rotations  Rotation: A transformation in which a figure is turned about a fixed point.  Center of Rotation: The fixed point on which a figure rotates on.  Angle of Rotation: The image formed from the rays drawn from the center of rotation.  In a coordinate plane, you can rotate figures more than 180°, here are some coordinate rules when you rotate figures about the origin. For rotation of 90 °, (a, b) (-b, a). For rotation of 180 °, (a, b) (-a, -b). For rotation of 270 °, (a, b) (b, -a).

9.4 Perform Rotations Continued YYYYou can also find certain images rotated about the origin using matrix multiplication Theorem 9.3: Rotation Theorem: A rotation is an isometry ° rotation counterclockwise ° rotation counterclockwise ° rotation counterclockwise ° rotation counterclockwise ° rotation counterclockwise ° rotation counterclockwise

Try This  Rotate points M(3, 2) and N(4, 8) 90 ° about the origin. M’(-2, 3) N’(-8, 4) M’(-2, 3) N’(-8, 4)  Rotate points X(9, 5) and Y(8, -7) 180 ° about the origin. X(-9, -5) Y(-8, 7) X(-9, -5) Y(-8, 7)  Rotate points D(5, -7) and E(-3, -3) 270 ° about the origin. D’(-7, -5) E(-3, 3) D’(-7, -5) E(-3, 3)

9.5 Apply Compositions of Transformations  Glide Reflection: A translation followed by a reflection.  Composition of a Transformation: When two or more transformations are combined to form a single transformation  Composition Theorem: The composition of two (or more) isometries is an isometry.

9.5 Apply Compositions of Transformations  Theorem 9.5: Reflections in Parallel Lines Theorem: If lines k and m are parallel, then a reflection in line k followed by a reflection in line m is the same as a translation.  Theorem 9.6: Reflections in Intersecting Lines Theorem: If lines k and m intersect at point p, then a reflection in k followed by a reflection in m is the same as a rotation about point p. The angle of rotation is 2x°, where x° is the measure of the acute or right angle formed by k and m.

Try This!  Graph triangle A(-8, 8) B(-3, 4) C(-2, 1), translate it using (x, y) (x+1, y+6) then reflect it over the x axis.  A’’(-7, -14) B’’(-2, -10) C’’(-1, -7)

9.6 Identify Symmetry  Line Symmetry: Part of a line that consists of two points, called endpoints, and all points on the line that are between the endpoints.  Line of Symmetry: The line of reflection in a symmetrical figure.

9.6 Identify Symmetry Continued  Rotational Symmetry: A figure that that can be mapped onto itself by a rotation of 180° or less about the center of the figure.  Center of Symmetry: The point in the center of a figure with rotational symmetry.  This figure has rotational symmetry:

Try This!  Does this figure have rotational symmetry? Yes

9.7 Investigate Dilations  Dilation: A transformation in which the original figure and its image are similar.  A dilation is a reduction if 0 1  Scalar Multiplication: The process of multiplying each element of a matrix by a real number or scalar.  This is an example of scalar multiplication with matrices:

Try This!  Find the scale factor of the dilation, then tell whether it is a reduction or an enlargement: Enlargement Scale Factor of 4  Multiply