+0  
 
0
7276
3
avatar

1) 

Suppose you rotate triangle ABC clockwise 90º. If ABC has vertices A (-2, 1), B (-1, 4), and C (2, 2), vertex C' is

 
 
2) 

Suppose you rotate triangle ABC clockwise 90º. If ABC has vertices A (-2, 1), B (-1, 4), and C (2, 2), vertex B' is (? , 1). (HintNote the direction of rotation.)

 
3) 

Use a rotation matrix to rotate figure DEFGH counterclockwise 90º. If the figure has coordinates D (1, 3), E (3, 2), F (1, -1), G (-3, -2), and H (-2, 2), the coordinates of E' are (-2, ?).

 
4)

Suppose you rotate triangle ABC counterclockwise 90º. If ABC has vertices A (-2, 1), B (-1, 4), and C (2, 2), vertex B' is ( ? , -1).

 Oct 16, 2014

Best Answer 

 #1
avatar+238 
+8

(1)the anwser of number 1 can be any point ,because you didnt tell me rotate around which point

 (rotate around point A ,C'(-1,-3)

   rotate around Point B C'(-3,1)

rotate around point C , the martix of point Cno change (2,2)

rotate around the origin , C'(-2,-2)

(2)file:///C:/Users/Public/Pictures/Sample%20Pictures/New%20folder%20(2)/133.htm

In numbe 2 , I guess  the image rotate around point (-1,1) clockwise 90 degrees  , so the marix of point B' is (2,1)

(3)the figure rotate around point H(-2,2)counterclockwise 90 degrees,then the marix of point E is (-2,7)

(4) the figure rotate around point C (2,2) clockwise 90 degrees ,then the martix of point B' is (0,-1) 

 Oct 16, 2014
 #1
avatar+238 
+8
Best Answer

(1)the anwser of number 1 can be any point ,because you didnt tell me rotate around which point

 (rotate around point A ,C'(-1,-3)

   rotate around Point B C'(-3,1)

rotate around point C , the martix of point Cno change (2,2)

rotate around the origin , C'(-2,-2)

(2)file:///C:/Users/Public/Pictures/Sample%20Pictures/New%20folder%20(2)/133.htm

In numbe 2 , I guess  the image rotate around point (-1,1) clockwise 90 degrees  , so the marix of point B' is (2,1)

(3)the figure rotate around point H(-2,2)counterclockwise 90 degrees,then the marix of point E is (-2,7)

(4) the figure rotate around point C (2,2) clockwise 90 degrees ,then the martix of point B' is (0,-1) 

quinn Oct 16, 2014
 #2
avatar+23245 
+5

If you use matrices:    (Sorry, but I don't know how to make real matrix symbols here.)

counter-clockwise matrix:  | cosθ   -sinθ |                         clockwise matrix:   |  cosθ    sinθ |                                                              | sinθ     cosθ |                                                     | -sinθ    cosθ |

 

1) Point (2,2) 90° clockwise:  |  cos 90°    sin 90° |    X    | 2 |                                                                                                               | -sin 90°    cos 90° |         | 2 |

2) Point (-1,4) 90° clockwise:  |  cos 90°    sin 90° |    X    | -1 |                                                                                                              | -sin 90°    cos 90° |          | 4 |

3) Point (3,2) 90° counter-clockwise:  |  cos 90°   -sin 90° |    X    | 3 |                                                                                                               | sin 90°     cos 90° |          | 2 |

4) Point (-1.4) 90° counter-clockwise:  |  cos 90°   -sin 90° |    X    | -1 |                                                                                                              | sin 90°     cos 90° |          |  4 |

If you have trouble with the matrices, please ask.

 Oct 16, 2014
 #3
avatar+128063 
+5

I believe these points are meant to be rotated around the origin....

1. For the first one....C is at (2,2)......rotating a point in the first quadrant 90 degrees clockwise reverses the coordinates and changes the sign on the original x coordinate.....so....(2, 2) becomes (2, -2)......

2. Rotating a point in the second quadrant 90 degrees clockwise reverses the coordinates and changes the sign on the original x coordinate . So, B= (-1,4) and B' = (4, 1)

3. Here, we're just doing the opposite of what we did in (2). E = (3, 2), so E' = (-2, 3)

4. Rotating a point in the second quadrant 90 degrees counter-clockwise reverses the coordinates and changes the sign on the  original y coordinate. So B = (-1, 4) and B' = (-4, -1).

 

 Oct 17, 2014

3 Online Users

avatar
avatar