1) Select the SLIDER tool. [icon]/images/ggb/toolbar/mode_slider.png[/icon]. Click anywhere in the white area off to the right. [br]2) Be sure "Number" is selected. Set min = 0, max = 10, increment = 0.1. Hit OK. [br][br]3) Repeat step (2) two more times. For each new slider you create, keep these same parameters. [br][br]4) In the algebra view (left), uncheck the bubbles off to the left to ONLY SHOW the sliders in the steps window (and not in the window off to the right). This will give us more room. [br][br]5) Your sliders should be named "a", "b", and "c". Slide each slider now so that a = 2, b = 5, and c = 6. [br][br][color=#0000ff]More directions continue below the applet. [/color]
6) Select the CIRCLE WITH CENTER AND RADIUS tool [icon]https://beta.geogebra.org/images/ggb/toolbar/mode_circlepointradius.png[/icon] . Use it to create a circle with radius [i]a[/i]. (Be sure to type "a" (without the " ") in the input box that appears. [br][br]7) Plot a point anywhere ON the circle you just created in step (6). [br][br]8) Construct another circle with radius [i]b[/i] [b]centered at the center of this circle.[/b][br][br]9) Construct a circle [b]centered at the point you plotted in step (8)[/b] that has radius = [i]c[/i]. [br][br]10) Plot the point at which the circles you constructed in steps (8) and (9) intersect.
Construct a triangle that has vertices located at the 3 points you see. Once you do, display the length of each side. What do you notice?
The side lengths of the triangle constructed are the values of the sliders! Thus, we can now control this triangle's side lengths through these 3 sliders.
Go to the "Steps" window. Now interact with all 3 sliders to create triangles (or not) whose sides have lengths [i]a[/i], [i]b[/i], and [i]c. [/i]What condition(s) cause a triangle to exist? Not to exist?
A triangle exists if all 3 inequalities below are true:[br][br][math]a+b>c[/math][br][math]a+c>b[/math][br][math]b+c>a[/math][br][br]In simpler terms, 3 segment lengths can serve as the sides of a triangle if the sum of the larger two sides is greater than the length of the 3rd side. [br][br][b]Teachers:[/b][br]This is one powerfully effective means for students to actively discover the Triangle Inequality Theorem for themselves!
[color=#0000ff]When you're done (or if you're unsure of something), feel free to check by watching the quick silent screencast below the applet.[/color]