$\phantom{XX} \operatorname{arc\,sin:}[-1, +1] \rightarrow [ - \pi / 2, \pi / 2 ]\phantom{XX}$ and $\phantom{XXX} \operatorname{arc\,cos:} [-1, + 1] \rightarrow [0, \pi[\phantom{XX}$ ,

the value of $\phantom{X}cos(\operatorname{arc\,sin} \dfrac{3}{5} + \operatorname{arc\,cos} \dfrac{4}{5})\phantom{X}$ is: