Explanation:
3.
the circumference of a circle is
2×pi×r
r = 4 cm
so, we know, the full circle circumference is
2×pi×4 = 8×pi = 25.13274123... cm
a.
the arc length of AB is the part of the whole circumference that corresponds to 95° out of the full 360° of a whole circle.
arc AB = 8×pi × 95/360 = pi × 95/45 = pi × 19/9 =
= 6.632251158... cm
b.
the perimeter of OAB (the "pie slice") is then the arc AB plus 2 radius lengths (from the end points on the arc to the center of the circle) :
pi × 19/9 + 2×4 = pi×19/9 + 8 = 14.632251158... cm