# Function Rkfstep - HP F2226A - 48GII Graphic Calculator User Manual

Graphing calculator.

The following screen shots show the RPN stack before and after application of
function RRK:
The value stored in variable y is 3.00000000004.

## Function RKFSTEP

This function uses an input list similar to that of function RKF, as well as the
tolerance for the solution, and a possible step ∆x, and returns the same input
list, followed by the tolerance, and an estimate of the next step in the
independent variable. The function returns the input list, the tolerance, and
the next step in the independent variable that satisfies that tolerance. Thus,
the input stack looks as follows:
After running this function, the stack will show the lines:
Thus, this function is used to determine the appropriate size of a time step to
satisfy the required tolerance.
The following screen shots show the RPN stack before and after application of
function RKFSTEP:
These results indicate that (∆x)
3:
{'x', 'y', 'f(x,y)'}
ε
2:
∆x
1:
3:
{'x', 'y', 'f(x,y)'}
ε
2:
1:
(∆x)
next
= 0.34049...
next
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