Page 155 - Excel for Scientists and Engineers: Numerical Methods

132 EXCEL: NUMERICAL METHODS

is 6.514. The exact value for the area under the curve is n4/15 = 6.494; the error
in the value returned by the custom function is 0.3%.

Figure 7-6. Portion of data table for calculation of area under a curve.
Note that rows 13-37 have been hidden.
(folder 'Chapter 07 Examples', workbook 'Area under Curve', worksheet 'Curve2 by worksheet')

Area between Two Curves
The area between two curves can be determined by using any of the
calculation methods described previously. The area is determined by the
absolute value of the difference between the two curves, as in equation 7-7.

There are several possibilities for the "area between two curves": the area can
either be bounded by the curves f(x) and g(x) between specified limits (for
example, the vertical lines x = a1 and x = bl in Figure 7-7) or by the two curves
f(x) and g(x) between two points where they cross (the points x = a2 and x = b2 in
Figure 7-7).