angle 3 = angle 8 = 75°
angle 11 = 105°
angle 11 = angle 4 + angle 13
105° = 2/3(angle 13) + angle 13
105 = 5/3 angle (13)
angle (13) = 63
2 angle (2) = angle (13)
angle (2) = 63/2
angle (2) = 31.5°
angle (5) = angle (13) = 63°
angle 8 = 75°
angle 11 = 105°
angle 13 = 63
angle 2 = 31.5
angle 5 = 63°