f(x) =∫ f ' (x) dx =4sin-1(x) + C
Now f(1/2) = 8 => 4 * sin-1(1/2) + C = 8
If f(x) is in radian,
C = 8 - 4 * sin-1(1/2) = 8-2π/3
f(x) = 4 * sin-1(1/2) + 8 -2π/3
If f(x) in degrees
=>4 *30 +C = 8 => C = -112
f(x) = 4sin-1(x) -112 , where f(x) is in degrees