Find the length of arc ac if ab is 12ft and has a degree of 60

S = r theta
Where s = arc length
R = radius
Theta = angle measure in radians.
If AB is the radius
S = 12* 60(pi/180)
S = 12 * pi/3
S = 4pi ft
S = 12.56 ft
If AB is the diameter
S = 6 * 60(pi/180)
S = 6 * pi/3
S = 2pi ft
S = 6.28 ft

The (pi/180) is the conversion factor from degrees to radians.

40 & 50 in the right corner are the complementary angles as when placed in a sum (added together) they make 90°