I am very much confused and frustrated at this point and would just like to understand what I'm doing wrong... This program is supposed to calculate a truncated value of sine using it's series expansion beginning at i = 1. At values under 20 degrees it compares almost exactly with the intrinsic sine function, but after that it's as much as .06-.23 off! This is my first course in programming in general, and I've been very good at Fortran thus far, but there's something I'm missing in this case... This is the program I have been trying to fix: program series implicit none real :: n_factorial, sin_x, x, v1, sum_1, n_1 integer :: n, i write (*,*) 'enter n' read (*,*) n write (*,*) 'enter x in degrees' read (*,*) x n_factorial = 1 sin_x = 0 x = ((x*3.1415926535898)/180) v1 = sin(x) DO i = 1, n n_1 = (2*i) - 1 n_factorial = n_factorial * n_1 sum_1 = (((-1)**(i-1)) * ((x**((2*i) - 1))/(n_factorial))) sin_x = sin_x + sum_1 END DO write (*,*) sin_x write (*,*) ' ' write (*,*) v1 end program series This is my first time posting on this site, and posting in general, I would infinitely appreciate the help in figuring out what's wrong!