HP 33s Scientific manual Accuracy of Integration, KeysDisplayDescription

Keys:	Display:	Description:
H	The current equation	Selects Equation mode.
	or   ! !
OLX	1%¾	Starts the equation.
`	1%2¾	The closing right parenthesis is
		required in this case.
qLX	1%2ª%¾
‘	1%2ª%	Terminates the equation.
	/	Checksum and length.
	/
‡		Leaves Equation mode.

Now integrate this function with respect to x (that is, X) from zero to 2 (t = 2).

Keys:Display:Description:

Ÿ{}	
0 ‘2	_
H	1%2ª%
X	!!
	≥ /
	) 

Selects Radians mode.

Enters limits of integration (lower first).

Displays the current equation. Calculates the result for Si(2).

Accuracy of Integration

Since the calculator cannot compute the value of an integral exactly, it approximates it. The accuracy of this approximation depends on the accuracy of the integrand's function itself, as calculated by your equation. This is affected by round–off error in the calculator and the accuracy of the empirical constants.

Integrals of functions with certain characteristics such as spikes or very rapid oscillations might be calculated inaccurately, but the likelihood is very small. The general characteristics of functions that can cause problems, as well as techniques for dealing with them, are discussed in appendix E.

Integrating Equations 8–5