HP 15c - Manual (Page 199)

Section 14: Numerical Integration 199
Find Si(2).
Key in the following subroutine to evaluate the function f(x) = (sin x) / x.
*
Keystrokes Display
|¥ 000–
Program mode.
´ b .2 001–42,21, .2 Begin subroutine with a b
instruction.
[ 002– 23 Calculate sin x.
® 003– 34 Since a value of x will be
placed in the Y-register by the
f algorithm before it
executes this subroutine, the
® operation at this point
will return x to the X-register
and move sin x to the Y-
register.
÷ 004– 10 Divide sin x by x.
| n 005– 43 32
Now key the limits of integration into the X- and Y-registers. In Radians
mode, press ´f .2 to calculate the integral.
Keystrokes Display
|¥ 0.4401
Run mode.
0 v
0.0000
Key lower limit into Y-
register.
2
2
Key upper limit, into X-
register.
| R 2.0000
(If not already in Radians
mode.)
´f .2 1.6054
Si(2).
*
If the calculator attempted to evaluate f(x) = (sin x)/x at x = 0, the lower limit of integration, it would
terminate with Error 0 in the display (signifying an attempt to divide by zero), and the integral could not
be calculated. However, the f algorithm normally does not evaluate functions at either limit of
integration, so the calculator can calculate the integral of a function that is undefined there. Only when the
endpoints of the interval of integration are extremely close together, or the number of sample points is
extremely large, does the algorithm evaluate the function at the limits of integration.