[the length of a circumference]=2*pi*r for r= 4 units [the length of a circumference]=2*pi*4--------------> 25.12 units
if a full circle (360°) has a length---------------------> 25.12 units arc for an angle of 72 °---------------------------> X X=72*25.12/360------------> 5.024 units
the answer is the length of the subtending arc for an angle of 72° is 5.024 units
