Explanation:
the arc lenght is usually described by the following formula:

where l is the arc length, alpha the angle(in radians) and r is the radius.
so in this case, using this formula we get

we are multiplying 75 x (pi/180) cuz, the angle has to be in radians. then

more sensible than the last result, considering that the total length of the circle is
L=2(pi)r
in this case L= 31.4 cm aprox