Swimming Fish
In this activity we use sliders to control the location of a point or a set of points.
Applet 1 shows a point and a slider.
Move the slider. The point doesn't move.
Now edit the value of the point: write A=(2+a,5) into the input bar.
The point should now move with the slider.
Notice the value of the slider and the value of the x coordinate.
Applet 1: Move the point left and right
Applet 2 shows a point and two sliders. The point is currently independent of the sliders. If you move either slider, the point doesn't move.
The input bar is at the bottom of the applet. Type A=(2+a,5+b) then press enter.
Now the x-coordinate changes with the slider value 'a'. The y-coordinate changes with the slider value 'b'. Press play to see the point move according to the slider values.
Alter the speed on each slider so that the point goes up and down a lot.
Alter the speed on each slider so that the point only goes up and down once as it travels across the screen.
Applet 2: Move the point in all four directions
Applet 3 shows a triangle and two sliders.
The triangle is defined by the points A, B and C. Points are defined using upper case letters. The points are hidden but the triangle is visible.
Type A=(2+a, 5+b) then press enter.
Type B=(1+a, 2+b) then press enter.
Type C=(4+a, 3+b) then press enter.
Now all three points will move with the slider values.
Press play to see the triangle move.
If the triangle deforms, examine each point to see if you typed it in correctly.
Applet 3: Animate a triangle
Applet 4 shows two sliders and a background picture of the fish.
Enter in each point to include a variable.
Type
A = (-2+a,2+b)
B = (-2+a,7+b)
keep going until you have typed in all the points of the fish.
Now use the polygon tool to join up all your points.
Press play to see if your fish moves without being deformed.
Applet 4: Animate the Fish
Applet 5 shows the fish and one slider named 'c'.
Imagine that the mouth opens and closes. Where does the point LIP go? Does the 'x' or the 'y' coordinate change? By how much?
Type LIP = (9+c, 3)
press play to see if this works.
Type LIP = (9, 3+c)
press play to see if this works.
The slider doesn't have the right minimum and maximum.
Edit the slider (kebab menu on the slider) so that the lip opens and closes.
Applet 5: Animate the mouth
Applet 6 shows three sliders and some construction tools.
Use the tools to create and animate a shape.
Applet 6: Make your own
Explain
The letter ‘a’ on the first slider is known as a variable as it is a number that changes. The value ‘2+a’ is an expression for the x coordinate of the point A in the first applet. Using the words ‘variable’ and ‘expression’ explain why the sliders control the animation.
Finally
If each task has worked out so far, return to your fish on applet 4.
Introduce a third slider to the applet, and make the mouth open and close.
Right click to graphics to turn off the axes and the grid.
Click the bullets beside the points to turn off points (don't turn off the eye!).
Somewhere in graphics, you can change the color of the background and the opacity of the fish. Its also possible to 'turn off' the background picture.
(Optional)
Applet 7 shows an animated fish with additional features. This was made using the geogebra app downloaded onto a desktop with a large monitor. https://www.geogebra.org/download
Click the link https://www.geogebra.org/m/chpswtpg. Use the menu to choose 'open in app'. From here you can right click on any object to explore any settings.