Angle sum in a triangle

Task

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

1.		Create a triangle ABC with counter clockwise orientation.
2.		Create the angles α, β and γ of triangle ABC.
3.		Create a slider for angle δ with Interval 0 ̊ to 180 ̊ and Increment 10 ̊.
4.		Create a slider for angle ε with Interval 0 ̊ to 180 ̊ and Increment 10 ̊.
5.		Create midpoint D of segment AC and midpoint E of segment AB.
6.		Rotate the triangle around point D by angle δ (setting clockwise). Hint: Enter δ by using the Virtual Keyboard.
7.		Rotate the triangle around point E by angle ε (setting counter clockwise). Hint: Enter ε by using the Virtual Keyboard.
8.		Move both sliders δ and ε to show 180 ̊.

9.	Create angle ζ using the points A’C’B’. Hint: To be sure to select the right vertices change angle δ or use the command angle(A’, C’, B’) instead.
10.	Create angle η using the points C'₁B'₁A'₁. Hint: To be sure to select the right vertices change angle ε before or use the command angle(C'₁, B'₁, A'₁) instead.
11.	Enhance your construction using the Style Bar. Hint: Congruent angles should have the same color.
12.	Create dynamic text displaying the interior angles and their values (e.g. enter `α =` and select α from the list of objects on tab of the Advanced section).
13.	Calculate the angle sum by entering `sum = α + β + γ` in the Input Bar.
14.	Insert the angle sum as a dynamic text: `α + β + γ =` and select sum from the list of objects on tab	Match colors of corresponding angles and text using the Style Bar.
16.	Fix all texts that are not supposed to be moved by using the Style Bar.