cos((3*sqrt(3)+4) /(5*sqrt(10))

Are you sure that your question is correct??

$$\\Cos\;\frac{(3\sqrt3+4)}{5\sqrt{10}}\\\\$$

If this angle is in radian then it =0.8355

if it is in degrees then it is.

$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\frac{\left({\mathtt{3}}{\mathtt{\,\times\,}}{\sqrt{{\mathtt{3}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{4}}\right)}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\sqrt{{\mathtt{10}}}}\right)}}\right)} = {\mathtt{0.999\: \!948\: \!477\: \!928}}$$

i would like an answer as previous: such as acos1/3

But inverse cos  (or acos) is where you have the ratio and your answer is an angle.

THIS one id the other way around.

You have the angle and you want the Cos ratio.  

that is why I think that there is an error in your question.