Press to access the arc length option which finds the length of a curve between two values.

Next, enter an expression, the variable, a start value, and an end value separated by commas. For example, to find the length of the curve y = x

`tol`

is used to determine how accurate to calculate
this integral. The TI tries to keep the absolute error under `tol`

.
A smaller value yields a more accurate integral but takes longer to compute.
It can be changed in the tolerance editor available by pressing
. Its
value is typically about 0.001.