module mymod
   implicit none
contains
   subroutine trans(u,v,a,u1,v1)
      real*8, intent(in)  :: u,v,a
      real*8, intent(out) :: u1,v1
      u1 = u*cos(a) - v*sin(a)
      v1 = u*sin(a) + v*cos(a)
      return
   end subroutine trans
end module mymod

program t
   use mymod
   implicit none
   real*8 u,v,a,u1,v1,u2,v2
   u=1
   v=2
   a=0.1d0
   print *,'u',u
   print *,'v',v
   call trans(u,v,a,u1,v1)
   print *,'u1',u1
   print *,'v1',v1
   call trans(u1,v1,-a,u2,v2)
   print *,'u2',u2
   print *,'v2',v2
end program t