OK thanks for your help. I think I got it. The effect of RealField is like creating a new number type. I need to make sure all my real are of the right type. It appears integers are fine as is.
Here is working code... def test(big): my_pi = RealField(big)(pi) ten = RealField(big)(10.0) constant = 100 * sqrt(my_pi/log(ten)) ten_thou = RealField(big)(10000.0) f(k) = ten^(-k^2/ten_thou) the_sum = RealField(big)(sum(f(k) for k in range(-big, big + 1))) difference = the_sum - constant return difference I can see difference getting smaller for test(1000), test(2000), test(3000), etc. cs -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org