cos

program test
implicit none

real :: angle, ret

    PRINT *, 'Enter an angle (in radian)'
    read *, angle
    print *,'real_cos(', angle, ') =', cos(angle) ! real cosinus
    call cos2(angle, 12, ret)
    print *,'cos(', angle, ') = ', ret ! cosinus calculate

end  program test

subroutine cos2(angle, n, ret)
    implicit none

    integer :: i, n, a, b
    real :: angle, ret

    a = 8*n - 6
    b = 2*n * (2*n - 1)

    ret = 1.000000

    do i = 1, n

        ret = 1 - (angle * angle * ret) / b
        b = b - a
        a = a - 8

    end do

    !return ret

end subroutine cos2