Page 206 - Excel for Scientists and Engineers: Numerical Methods

CHAPTER 8 ROOTS OF EQUATIONS 183

must repeat the action of goal-seeking each time you change any of the
parameters.
A limitation of the GoalSeek custom function is that fargetcell must contain
the complete expression dependent on changing-cell. Only the instances of
changing-cell that appear in the formula in targef-cell will be used in the
Newton-Raphson calculation.

300
250

200
> 150
100

50
0
-50 1 5 10 15

X

Figure 8-42. The value of x that makes the function y = x2 + 6x - 10 have the value 210.
(folder 'Chapter 08 Examples', workbook 'Goalseek Fn'. sheet 'Intersection of line with h (2)')
The CD contains an example of the use of the GoalSeek function to find
approximately 180 intersection points of lines with a curve in a chart (see folder
'Chapter 08 Examples', workbook 'Diatomic Molecule', sheet 'Vibrational Energy
Levels'). The resulting chart is shown in Figure 8-43. The chart contains two
data series. The first data series shows the continuous function of energy as a
function of distance r. The second data series shows the approximately 90
horizontal vibrational energy levels.