Create an interactive figure that allows your students to explore the angle sum in a triangle.

[table][tr][td]1.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_polygon.png[/icon][/td][td]Create a triangle [i]ABC[/i] with counter clockwise orientation.[/td][/tr][tr][td]2.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_angle.png[/icon][/td][td]Create the angles [i]α[/i], [i]β[/i] and [i]γ[/i] of triangle [i]ABC[/i].[/td][/tr][tr][td]3.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_slider.png[/icon][/td][td]Create a slider for angle [i]δ[/i] with Interval 0 ̊ to 180 ̊ and [i]Increment[/i] 10 ̊.[/td][/tr][tr][td]4.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_slider.png[/icon][/td][td]Create a slider for angle [i]ε[/i] with Interval 0 ̊ to 180 ̊ and [i]Increment[/i] 10 ̊.[/td][/tr][tr][td]5.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_midpoint.png[/icon][/td][td]Create midpoint [i]D[/i] of segment [i]AC[/i] and midpoint [i]E[/i] of segment [i]AB[/i].[/td][/tr][tr][td]6.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_rotatebyangle.png[/icon][/td][td]Rotate the triangle around point [i]D[/i] by angle [i]δ[/i] (setting [i]clockwise[/i]).[br][b]Hint:[/b] Enter [i]δ[/i] by using the [img]https://wiki.geogebra.org/uploads/thumb/c/ce/Baseline-keyboard-24px.svg/24px-Baseline-keyboard-24px.svg.png[/img] V[i]irtual Keyboard[/i].[/td][/tr][tr][td]7.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_rotatebyangle.png[/icon][/td][td]Rotate the triangle around point [i]E[/i] by angle [i]ε[/i] (setting [i]counter clockwise[/i]).[br][b]Hint:[/b] Enter [i]ε[/i] by using the [img]https://wiki.geogebra.org/uploads/thumb/c/ce/Baseline-keyboard-24px.svg/24px-Baseline-keyboard-24px.svg.png[/img] V[i]irtual Keyboard[/i].[/td][/tr][tr][td]8.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_move.png[/icon][/td][td]Move both sliders [i]δ[/i] and [i]ε[/i] to show 180 ̊.[/td][/tr][/table]

[table][tr][td]9.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_angle.png[/icon][/td][td]Create angle ζ using the points [i]A’C’B’.[br][/i][b]Hint:[/b] To be sure to select the right vertices change angle [i]δ[/i] or use the command [i]angle(A’, C’, B’)[/i] instead.[br][/td][/tr][tr][td]10.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_angle.png[/icon][/td][td]Create angle η using the points[i] C'[sub]1[/sub]B'[sub]1[/sub]A'[sub]1[/sub][/i].[br][b]Hint:[/b] To be sure to select the right vertices change angle [i]ε[/i] before or use the command [i]angle(C'[sub]1[/sub], B'[sub]1[/sub], A'[sub]1[/sub])[/i] instead.[/td][/tr][tr][td]11.[/td][td][img]https://wiki.geogebra.org/uploads/thumb/d/db/Stylingbar_icon_graphics.svg/32px-Stylingbar_icon_graphics.svg.png[/img][/td][td]Enhance your construction using the [i]Style Bar[/i].[br][b]Hint:[/b] Congruent angles should have the same color.[/td][/tr][tr][td]12.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_text.png[/icon][/td][td]Create dynamic text displaying the interior angles and their values (e.g. enter [code]α = [/code]and select α from the list of objects on tab [img]https://wiki.geogebra.org/uploads/thumb/4/4e/Geogebra-logo-elipse.svg/16px-Geogebra-logo-elipse.svg.png[/img] of the [i]Advanced [/i]section).[/td][/tr][tr][td]13.[/td][td][icon]https://wiki.geogebra.org/uploads/thumb/4/40/Menu_view_algebra.svg/120px-Menu_view_algebra.svg.png[/icon][/td][td]Calculate the angle sum by entering [code]sum = α + β + γ[/code] in the [i]Input Bar[/i].[/td][/tr][tr][td]14.[/td][td][icon]https://www.geogebra.org/images/ggb/toolbar/mode_text.png[/icon][/td][td]Insert the angle sum as a dynamic text: [code]α + β + γ =[/code] and select [i]sum [/i]from the [i][/i]list of objects on tab [img]https://wiki.geogebra.org/uploads/thumb/4/4e/Geogebra-logo-elipse.svg/16px-Geogebra-logo-elipse.svg.png[/img].[/td][/tr][tr][td]15.[/td][td][img]https://wiki.geogebra.org/uploads/thumb/d/db/Stylingbar_icon_graphics.svg/32px-Stylingbar_icon_graphics.svg.png[/img][/td][td]Match [img]https://www.geogebra.org/wiki/uploads/thumb/f/ff/Stylingbar_color_blue.svg/16px-Stylingbar_color_blue.svg.png[/img] colors of corresponding angles and text using the [i]Style Bar[/i]. [/td][/tr][tr][td]16.[/td][td][img]https://wiki.geogebra.org/uploads/thumb/d/db/Stylingbar_icon_graphics.svg/32px-Stylingbar_icon_graphics.svg.png[/img][br][/td][td][img]https://www.geogebra.org/wiki/uploads/thumb/9/92/Stylingbar_object_unfixed.svg/16px-Stylingbar_object_unfixed.svg.png[/img] Fix all texts that are not supposed to be moved by using the [i]Style Bar[/i].[/td][/tr][/table]