Warm-Up Reflect triangle ABC across the line y = 1 given A(0,3) , B(-1, 5) , and C(-4, 2). List the coordinates of the image: A’( , ) B’( , ) C’( , ) Put homework questions on the board!
A. B. C. D. 1. Which of the following shows a reflection in the x-axis? 2. Triangle PQR is shown below. What is the image of point R after a reflection over the line y=x? A. B. C. D. Plickr?
9.1 Summary Reflect over x-axis (x , y) Reflect over y-axis (x , y) Reflect over y=x
9.3 Rotations Objectives: Make rotations about a point in the coordinate plane. Know the relationship between reflections and rotations.
Clockwise Counterclockwise 90° 180° 270° versus Counterclockwise 90° 180° 270° clockwise counterclockwise counterclockwise
Is a rotation an isometry? Rotation about a point. Is a rotation an isometry? angle of rotation P P image preimage center of rotation
Example 1: Perform the following rotations on point A. Rotate 90 degrees counterclockwise about the origin: Rotate 180 counterclockwise Rotate 270 degrees counterclockwise A(-2,3) (-3, -2) (2, -3) (3, 2)
Strategies for Rotations: Measure the angle of rotation Memorize the rules Physically rotate your paper
Example 2: DRST has coordinates R(-2, 3), S(0, 4), and T(3, 1). If DRST is rotated 90° counter clockwise about the origin, what are the new coordinates?
Example 3: A quadrilateral ABCD has the following vertices: A(2, -2) B(4, 1), C(5, 1), D(5, -1). Rotate ABCD 270° counterclockwise about the origin and name the coordinates of the new vertices.
Example 4: A quadrilateral has a vertices P(3, -1) Q(4, 0), R(4, 3), and S(2, 4). Rotate PQRS 180°counterclockwise about (0,0) and name the coordinates of the new vertices.
Take your partner’s notes Draw any polygon on their coordinate plane Create your own! Take your partner’s notes Draw any polygon on their coordinate plane Tell them how many degrees to rotate it Check your partner’s work! More Example is if necessary
9.1, 9.3 Summary Reflect over x-axis (x , y) (x, -y) Reflect over y-axis (x , y) (-x, y) Reflect over y=x (x , y) (y , x) Rotate 90 degrees CCW (x, y) (-y, x) Rotate 180 degrees CCW (x, y) (-x, -y) Rotate 270 degrees CCW (x, y) (y, -x)
Triangle PQR is shown below Triangle PQR is shown below. What is the image of point Q after a 90° counterclockwise rotation about the origin? A. (–5, –4) B. (–5, 4) C. (5, 4) D. (4, –5)
The coordinates of quadrilateral ABCD before and after a rotation about the origin are shown in the table. Find the angle of rotation. A. 90° clockwise B. 90° counterclockwise C. 180° clockwise D. 45° clockwise
Describe the transformations used to map the figure in the left column onto each of the figures in the right column. If Time
1. Hexagon DGJTSR is shown below 1. Hexagon DGJTSR is shown below. What is the image of point T after a 90 counterclockwise rotation about the origin? 2. The coordinates of triangle XYZ before and after a rotation about the origin are shown in the table. Find the angle of rotation. Exit Card A. 180° clockwise B. 270° clockwise C. 90° clockwise D. 90° counterclockwise
Geometry All rotations are COUNTER CLOCKWISE Homework: p.644-646 #15-18, 37, 39, 40 All rotations are COUNTER CLOCKWISE