The principal value of $\cos^{-1}(\cos\frac{2π}{3})+\sin^{-1}(\sin\frac{2π}{3})$ is:

$π$ $\frac{π}{2}$ $\frac{π}{3}$ $\frac{4π}{3}$

$π$

$\cos^{-1}(\cos\frac{2π}{3})+\sin^{-1}(\sin\frac{2π}{3})$ $\frac{2π}{3}+(π-\frac{2π}{3})$  {since $\frac{2π}{3}>\frac{π}{2}$ and domain of $\sin^{-1}x$ is $x∈[-\frac{π}{2},\frac{π}{2}]$} $=π$