Lesson 10-5: Transformations 1 Lesson 10-5 Transformations

Lesson 10-5: Transformations 2 Types of Transformations Reflections: These are like mirror images as seen across a line or a point. Translations ( or slides): This moves the figure to a new location with no change to the looks of the figure. Rotations: This turns the figure clockwise or counter-clockwise but doesn’t change the figure. Dilations: This reduces or enlarges the figure to a similar figure.

Lesson 10-5: Transformations 3 Reflections You could fold the picture along line l and the left figure would coincide with the corresponding parts of right figure. l You can reflect a figure using a line or a point. All measures (lines and angles) are preserved but in a mirror image. Example:The figure is reflected across line l.

Lesson 10-5: Transformations 4 Reflections – continued… reflects across the y axis to line n (2, 1)  (-2, 1) & (5, 4)  (-5, 4) Reflection across the x-axis: the x values stay the same and the y values change sign. (x, y)  (x, -y) Reflection across the y-axis: the y values stay the same and the x values change sign. (x, y)  (-x, y) Example:In this figure, line l : reflects across the x axis to line m. (2, 1)  (2, -1) & (5, 4)  (5, -4) ln m

Lesson 10-5: Transformations 5 Reflections across specific lines: To reflect a figure across the line y = a or x = a, mark the corresponding points equidistant from the line. i.e. If a point is 2 units above the line its corresponding image point must be 2 points below the line. (-3, 6)  (-3, -4) (-6, 2)  (-6, 0) (2, 3)  (2, -1). Example: Reflect the fig. across the line y = 1.

Lesson 10-5: Transformations 6 Lines of Symmetry If a line can be drawn through a figure so the one side of the figure is a reflection of the other side, the line is called a “line of symmetry.” Some figures have 1 or more lines of symmetry. Some have no lines of symmetry. One line of symmetry Infinite lines of symmetry Four lines of symmetry Two lines of symmetry No lines of symmetry

Lesson 10-5: Transformations 7 Translations (slides) If a figure is simply moved to another location without change to its shape or direction, it is called a translation (or slide). If a point is moved “a” units to the right and “b” units up, then the translated point will be at (x + a, y + b). If a point is moved “a” units to the left and “b” units down, then the translated point will be at (x - a, y - b). A B Image A translates to image B by moving to the right 3 units and down 8 units. Example: A (2, 5)  B (2+3, 5-8)  B (5, -3)

Lesson 10-5: Transformations 8 Rotations An image can be rotated about a fixed point. The blades of a fan rotate about a fixed point. An image can be rotated over two intersecting lines by using composite reflections. Image A reflects over line m to B, image B reflects over line n to C. Image C is a rotation of image A. A B C m n

Lesson 10-5: Transformations 9 Rotations It is a type of transformation where the object is rotated around a fixed point called the point of rotation. When a figure is rotated 90° counterclockwise about the origin, switch each coordinate and multiply the first coordinate by -1. (x, y)  (-y, x) When a figure is rotated 180° about the origin, multiply both coordinates by -1. (x, y)  (-x, -y) Ex: (1,2)  (-1,-2) & (6,2)  (-6, -2) Ex: (1,2)  (-2,1) & (6,2)  (-2, 6)

Lesson 10-5: Transformations 10 Dilations A dilation is a transformation which changes the size of a figure but not its shape. This is called a similarity transformation. Since a dilation changes figures proportionately, it has a scale factor k. If the absolute value of k is greater than 1, the dilation is an enlargement. If the absolute value of k is between 0 and 1, the dilation is a reduction. If the absolute value of k is equal to 0, the dilation is congruence transformation. (No size change occurs.)

Lesson 10-5: Transformations 11 Dilations – continued… In the figure, the center is C. The distance from C to E is three times the distance from C to A. The distance from C to F is three times the distance from C to B. This shows a transformation of segment AB with center C and a scale factor of 3 to the enlarged segment EF. In this figure, the distance from C to R is ½ the distance from C to A. The distance from C to W is ½ the distance from C to B. This is a transformation of segment AB with center C and a scale factor of ½ to the reduced segment RW. C E A F B C R A B W

Lesson 10-5: Transformations 12 Dilations – examples… Find the measure of the dilation image of segment AB, 6 units long, with a scale factor of 1. S.F. = -4: the dilation image will be an enlargment since the absolute value of the scale factor is greater than 1. The image will be 24 units long. 2.S.F. = 2/3: since the scale factor is between 0 and 1, the image will be a reduction. The image will be 2/3 times 6 or 4 units long. 3.S.F. = 1: since the scale factor is 1, this will be a congruence transformation. The image will be the same length as the original segment, 1 unit long.