program func                                
!demonstrates use of user defined functions
     implicit none
     integer, parameter :: ikind=selected_real_kind(p=15)
     real (kind=ikind):: deg,rads
     print *, 'Enter an angle in degrees'
     read  *, deg
     write(*,10) 'sin = ',sin(rads(deg))
     write(*,10) 'tan = ',tan(rads(deg))
     write(*,10) 'cos = ',cos(rads(deg))
10   format(a,f10.8)
     end program func
!_____________________________________________
     function rads(degrees)
     implicit none
     integer, parameter :: ikind=selected_real_kind(p=15)
!    returns radians
     real (kind=ikind) :: pi,degrees,rads
     pi=4.0_ikind*atan(1.0_ikind)
     rads=(degrees*pi/180.0_ikind)
     end function rads