Cos(4/10) in minutes and seconds?

I think you want to find an angle that has the cosine value of 4/10

We can use the cosine inverse for this

arccos (4/10)  ≈  66.42°

Converting this to  D-M-S  we have

.42°  =  (.42*60) minutes =  25.2 minutes

.2 minutes  = ( .2* 60 ) seconds  = 12 seconds

So 

66.42°  =  66° 25' 12"