$ gfortran -Wall -Wextra -o out marvin1.f90
marvin1.f90:4.36:

real :: rise, run, theta, deg_to_rad, rad, pi
                                    1
Warning: Unused variable 'deg_to_rad' declared at (1)
$ ./out
 pi is   3.14159274    
 rise is   0.421622515    
$ cat marvin1.f90
program main
implicit none

real :: rise, run, theta, deg_to_rad, rad, pi

run = 3.0
theta = 8.0

pi = 4.0*atan(1.0)
print *,"pi is", pi

rad = theta * pi / 180.0

rise = run * tan (rad)

print *, "rise is ", rise

end program main
! gfortran -Wall -Wextra -o out marvin1.f90
$