If angle AED is 90 degrees and angle AEB is 60 degrees. Subtract 60 from 90. Since BEC and CED are equal, the difference of 60 minus 90 (30) divided by two is the sum. 60 + 15 +15 = 90. BEC and CED equal 15 degrees. Good luck.
The external angle between the secants (20°) is half the difference of the intercepted arcs.
(75° - B)/2 = 20°
75° - B = 40°
75° - 40° = B = 35°
You can use the Pythagoras theorem for this since a right triangle is formed.
C = 12
A = 4
B = x
Input values:
So, about 11ft.
I'm pretty sure its constant