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

The cosine of anything can't be equal to 54 !!!

I just evaluated what the questioner asked......in fact....I "pasted" it directly into the onsite calculator....!!!

The expression in the parentheses evaluates to about 0.58161574731657

If this is degree measure, we have

cos(0.58161574731657) = about .9990  (almost 1, since this is close to 0 degrees)

If this is radian measure, we have

cos(0.58161574731657) = about .836

but my answer for this questin is 54?????

I wish you had not asked the same question twice - it causes confusion.