# Finding cumulative distribution function, given density function using integration

I am trying to find the cumulative distribution function given the following density function: $$f_X(x)= begin{cases} frac{2}{3sqrt{x}}, &0leq x < frac{9}{16}\ 0, &text{otherwise.} end{cases}$$
I know I need to integrate $$f_X(x)$$ to find $$F_X(x)$$ but I am unsure what the initial value for this integral must be. Would this be correct integral, $$intlimits_{0}^{x}f_X(x)dx=frac{4sqrt{x}}{3}=F_X(x)$$?