Texas Instruments TI-83 PLUS - Manual (Page 74)

TI-83 Plus Math, Angle, and Test Operations 71
fnInt(
fnInt( (function integral) returns the numerical integral (Gauss-Kronrod
method) of expression with respect to variable , given lower limit, upper limit,
and a tolerance (if not specified, the default is 1 âL 5). fnInt( is valid only for
real numbers.
fnInt( expression , variable , lower , upper [ , tolerance ] )
Tip: To speed the drawing of integration graphs (when fnInt( is used in a Y=
equation), increase the value of the Xres window variable before you press
s .