Grade 8 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.
Edit the point so that the first slider controls movement left and write, and the second slider controls movement up and down. Write A=(2+a,5+b) into the input bar.
Alter the values on the sliders so that the point goes up and down alot.
Alter the values on the 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.
Edit the points so that all three x values say ' +a' and all three y values say '+b'.
Applet 3: Animate a triangle
Applet 4 shows the fish and no sliders.
Imagine that the mouth closes. Where does the point LIP go? Does the 'x' or the 'y' coordinate change? By how much?
Use the slider tool to create a slider. Set the minimum and the maximum to the correct values for the LIP to open and close.
Edit the point LIP=(9,3) to include the slider. Press play to see if it works.
Applet 4: Animate the mouth
Applet 5 shows the fish with two sliders.
Edit each point in this way: A = (2+a,2+b)
or in this way: A = (2,2)+(a,b)
or create a point called GO (any name with upper case letters works), and edit like this: A = (2,2)+GO
Create a slider for the mouth as you did in applet 4.
Applet 5: Animate the Fish
Applet 6 shows two sliders and the toolbar.
Use the tools to create and animate a shape.
You may add as many sliders as you need.
As 'reset' isn't available, you'll need to use the 'undo' or 'delete' to remove unwanted creations.
Applet 6: Make your own
Applet 7 shows an animated fish with additional features.
Click the link https://www.geogebra.org/m/chpswtpgto open the original, and use the menu to choose 'open in app'. From here you can right click on any object to see settings and to reverse engineer the applet.
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.