Tan(12) = 40/d
d = 40/tan(12)
d = 188.19m
6 times 20 equals 120 and equals 26 when added together
It was would numbers 000-000-0000 through 999-999-9999. So that would be 9,999,999,999 + 1 = 10 billion different 10-digit phone numbers.
Your octagon has a central angle of 360 deg. Since you're speaking of an octagon, which implies that the octagon is made up of eight triangles, divide 360 deg by 8 to obtain the measure of each minor arc formed.
