The geogebra activity here https://www.geogebra.org/m/dP7BAuZy#material/NAgxehQb shows a spinning windmill. This page will show you how to create animations like this, step by step.
In the microworld below, scroll on the the left bar until you see "Point O". [br]Click on "Point O", "Point A", "Point B", and "Point C" and see what happens.
To make this geogebra, I created points A, B, C and then created triangle [ABC] using the polygon tool.[br]Then I renamed it "[b][u]blade_shape[/u][/b]". To see where this is, click on the left cell for [u]blade_shape[/u] and see it hide and unhide.[br][br]The slider t shows angles in radians. [br][br]Then I used the tool "Rotate around point" to rotate "blade_shape" around point A by angle measure t. To do this, I did the following:[br][list][*]clicked on the "rotate around point" tool[/*][*]clicked on the middle of the the triangle [b][u]blade_shape[/u][/b][/*][*]clicked on the point A [/*][*]typed "t"[br][/*][/list]This created the triangle [A'B'C'], which I named [b][u]blade[/u][/b]. [br][br]See what happens when you click on the [b][u]blade[/u][/b] cell on the left column.[br][br]If you click the play button for the slider for t, you will see the blade go back and forth if you wait long enough. But that's not what a windmill does! A windmill should keep going.[br][br]To see how this works, [br][list][*]go to the link https://www.geogebra.org/geometry/fgf8rupz[/*][*]scroll up the left bar until you see the slider t. [/*][*]open up the "settings" for the slider t (in the left bar, click on the three dots next to the slider)[br][/*][*]change the "repeat" option from "oscillating" to "increasing"[/*][*]Now try pressing "play" again and see the windmill keep rotating the same direction![/*][/list]
Windmills typically have more than one blade. [br][br]We can create more blades by using the "Rotate around point" tool. Here's what I did:[br][list][*]clicked on the "rotate around point" tool[/*][*]clicked on the middle of the the triangle [b][u]blade[/u][/b][/*][*]clicked on the point A [/*][*]typed "90°"[/*][/list]This created the shape [u][b]blade'[/b][/u].[br][br]To see this shape, scroll until you can click on the[b] [u]blade'[/u][/b] cell on the left. You can do this here as well as in the geogebra link you were just using.
To keep creating more blades, I took each newly created blade and followed the same steps. For example:[br][list][*]click on the "rotate around point" tool[/*][*]click on the middle of the the triangle [b][u]blade'[/u][/b][/*][*]click on the point A [/*][*]type "90°".[/*][/list]To make all the blades visible, click on [u]blade'[/u], [u]blade''[/u], and [u]blade'''[/u] on the left.[br]Now press play.
How would you create an animation like this, but with 5 blades?
Follow the same steps to create a blade_shape and blade, where blade is blade_shape rotated by angle measure T about point A. [br]Then, when creating blade', blade'', etc., rotate each image by (360/5)° instead of 90° (which is (360/4)°).[br](Rotate blade by (360/5)° around A, then blade' by (360/5)° around A, then blade'' by (360/5)° around A, and keep going until you have enough blades.)
How would you create an animation like this, but with 5 blades and a non-isosceles triangle shaped blade?
First, select points to make your blade shape that are not in an isosceles triangle. For example, you might define 4 points A, B, C, D and then create polygon [ABCD], and then name this polygon blade_shape.[br]Or you might define 3 points A, B, C that do not form the vertices of an isosceles triangle and then create [ABC], then name that blade_shape. [br](You don't need to name it blade_shape; you can name it whatever you want. It can be helpful to name things to help you keep track of your intention.)[br]Then follow the same steps as above.
In the windmill animation example at https://www.geogebra.org/m/dP7BAuZy#material/NAgxehQb they used a different technique. If you're interested, read on. Otherwise, if the above is good enough for you, you can stop here.[br][br]To follow along, open a copy of the below geogebra here: https://www.geogebra.org/geometry/mpgwzqz6
To create the above, I did the following:[br][list][*]Create slider T from 0 to 2pi[/*][*]Define point A[/*][*]Define point B[/*][*]Use the tool "Circle with center" create a circle with center A going through B[/*][*]Use the tool "Angle with given size" to create an angle of measure T: click on tool, click on B, click on A, type "T". This creates point B' so that angle BAB' has directed angle measure T radians.[/*][*]Create a smaller circle around B'.[/*][/list]
Next, go to the copy of this and:[br][list][*]Create two points C and D, at each of the intersection points of the small circle and big circle. [/*][*]Create a polygon [ACD][/*][*]Rotate [ACD] about A by 120°[/*][*]Rotate [A'C'D'] about A by 120°[/*][/list]Finalize your animation by hiding what you don't want to see (by clicking the left cells), making the colors what you want, and switching the animation setting for the slider from Oscillating to Increasing (or Decreasing)!
If you click the play button for the slider for t, you will see the blade go back and forth if you wait long enough. But that's not what a windmill does! A windmill should keep going.[br][br]To see how this works, [br][list][*]go to the link https://www.geogebra.org/geometry/fgf8rupz[/*][*]scroll up the left bar until you see the slider t. [/*][*]open up the "settings" for the slider t (in the left bar, click on the three dots next to the slider)[br][/*][*]change the "repeat" option from "oscillating" to "increasing"[/*][*]Now try pressing "play" again and see the windmill keep rotating the same direction![/*][/list]