Rotation and Reflection Question

Anthony Dove shared this question 5 years ago
Answered

I have a question that I hope someone can answer regarding transformations. When I do a reflection or rotation of an object, Geogebra creates two new vertices for the image. I've attached an image to show what I mean. I follow the typical instructions. For example to create the 90-degree rotation about the origin in the image, I clicked and dragged to highlight quadrilateral ABCD, then I clicked on the origin, and then I entered 90 degrees counterclockwise. I would expect this to produce A', B', C', and D'. I do not want A_1', B_1', C_1', and D_1' to be created at the same time as it is redundant. Normally I just delete the second set of points, but I am tired of doing that and telling my students to do that as well. Any suggestions are greatly appreciated!

Comments (4)

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When you do a rotation of an object (eg : poly1),

define poly1=[{A,B,C,D,E}], with {...} , and only poly1' is created without A',B', ...

With tools, select poly1 in algebra view, no in graphic.

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I knew you could do it the Algebra view, but can you do it in the Graphic view as that is the more intuitive method? I'm trying to determine if this is a "glitch" when doing it graphically that could be reported to those who make the updates, or if there is some other issue with it that I am not aware.

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With the following command :


Polygon[F, G, H, I]


it works properly but not if you select the polygon in the graphic screen, so you should select the polygon in the algebric screen (to avoid A_1', B_1', ... ).

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Maybe your problem is that you are NOT working with a polygon, but with four points. And maybe you are rotating not only the points but also the segments. that would explain it: GG could be creating A', B', C' and D' for the points and A'_1, B'_1, C'_1 and D'_1 for the extreme points of the segment.


My advice is to use the Polygon tool/command and rotate/reflect/transform the Polygon (that will create the image for the polygon and its vertices and sides, all at once)

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