Approximate a sum with the default tolerances:
Find the error versus the exact value of
:
The error with smaller absolute and relative tolerances:
The error with larger absolute and relative tolerances:
Get the number of evaluation points used in a numerical summation:
The evaluation points used in a summation approximated by an integration method:
The evaluation points used in a summation approximated by the sequence extrapolation method:
Use a method for alternating series to get a very precise sum approximation:
The error from the exact result computed by
Sum:
The error using the default method:
By default
NSum uses 15 terms at the beginning before approximating the tail:
The error for this example is large because the summand peaks at 20:
Increasing
to include this feature improves the approximation:
By default the summand's convergence is verified:
Generally, if the convergence is not verified the summation is faster:
Approximate the formal sum without verifying convergence:
This is roughly equivalent to the formal symbolic result:
Use higher precision to get a better approximation:
Find the error versus the exact value of
:
can be used to evaluate multidimensional sums. 
:
:
is large:
:
EXAMPLES
Basic Examples 
Scope 