See attachment before reading.
PART 1: angles around D
PART 2: angles in triangle DCE
PART 3: x = x
PART 4: Returning to angles around D
Feel free to ask any question if something is unclear
I have a solution, but I'm sure someone will find a shorter one.
Find: .Code:A o * * * * 30° * * * * * * * * E * * α o * * * * * θ *α * x * B o * * * * * * * o * * * o C D
Since is isosceles,
. . Hence: . .
. . Hence: .
In isosceles triangle
Then: . .
At vertex , we have: .
Substitute  and : .
. . Therefore: .
thank you guys for the help.
But i think unforturnally this one was a little bit over my skill.
I understand your explanation in the beginning, but then its to mutch for me. I have just started the math course so hopfully i will understand it later on.
But thank you for your time anyway, maybe I come back another day with new questions.
Have a nice day