arcsin3/5=m
cosm=4/5
arctan2=n
sinn=2/√5
cosn=1/√5
sin(2n)=4/25
cos(2n)=√609/25
cos(arcsin3/5+2arctan2)=
=(4/5)*(√609/25) - (3/5)*(4/25) = (4√609-12)/125