program chebyshev

real    :: x,a,t,tMenos1,tMenos2
integer :: N


!================ Inicializo  ====================
N = 8
x = cos(1.3)
a = 1.3
print *, "a = ",a
print *, "x = cos(a) =  ",x
print *, "------------------------------------------------"
print *,

do n = 0,N,2
  if ( n==0 ) then
     t = 1
  else
     tMenos2 = 1
     tMenos1 = x
     do i = 1,n-1
        t = 2*x*tMenos1 - tMenos2
        tMenos2 = tMenos1
        tMenos1 = t
     end do

  end if
  print *, "n = ",n
  print *, "cos(n*a) = ",cos(n*a)
  print *, "cheb_n_(cos(a)) = ",t
  print *,
end do
end program chebyshev