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. [br][br]Move the slider. The point doesn't move.[br][br]Now edit the value of the point: write A=(2+a,5) into the input bar.[br][br]The point should now move with the slider. [br][br]Notice the value of the slider and the value of the x coordinate.
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.[br][br]The input bar is at the bottom of the applet. Type A=(2+a,5+b) then press enter.[br][br]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.[br][br]Alter the speed on each slider so that the point goes up and down a lot.[br]Alter the speed on each slider so that the point only goes up and down once as it travels across the screen.
Applet 3 shows a triangle and two sliders.[br][br]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.[br][br]Type A=(2+a, 5+b) then press enter.[br]Type B=(1+a, 2+b) then press enter.[br]Type C=(4+a, 3+b) then press enter.[br][br]Now all three points will move with the slider values. [br][br]Press play to see the triangle move.[br][br]If the triangle deforms, examine each point to see if you typed it in correctly.
Applet 4 shows two sliders and a background picture of the fish.[br][br]Enter in each point to include a variable. [br][br]Type [br]A = (-2+a,2+b)[br]B = (-2+a,7+b)[br][br]keep going until you have typed in all the points of the fish.[br][br]Now use the polygon tool to join up all your points.[br][br]Press play to see if your fish moves without being deformed.
Applet 5 shows the fish and one slider named 'c'.[br][br]Imagine that the mouth opens and closes. Where does the point LIP go? Does the 'x' or the 'y' coordinate change? By how much?[br][br]Type LIP = (9+c, 3)[br]press play to see if this works.[br]Type LIP = (9, 3+c)[br]press play to see if this works.[br][br]The slider doesn't have the right minimum and maximum.[br]Edit the slider (kebab menu on the slider) so that the lip opens and closes.
Applet 6 shows three sliders and some construction tools.[br][br]Use the tools to create and animate a shape.
The letter ‘a’ on the first slider is known as a [i]variable[/i] as it is a number that changes. The[br]value ‘2+a’ is an [i]expression [/i]for the x coordinate of the point A in the first applet. [br][br]Using the words ‘variable’ and ‘expression’ explain why the sliders control the animation.
If each task has worked out so far, return to your fish on applet 4.[br][br]Introduce a third slider to the applet, and make the mouth open and close.[br][br]Right click to graphics to turn off the axes and the grid.[br][br]Click the bullets beside the points to turn off points (don't turn off the eye!).[br][br]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.[br][br]
Click the link [url=https://www.geogebra.org/m/chpswtpg]https://www.geogebra.org/m/chpswtpg[/url]. This diagram is an elaboration of the fish above. Use the menu to choose 'open in app'. From here you can right click on any object to explore any settings.[br]