HP 15C Manuale Utente Scaricare il pdf (Pagina 227)

Appendix D: A Detailed Look at _ 227

Special consideration is required for a different

type of situation in which _ finds a root

with a nonzero function value. If your

function's graph has a discontinuity that

crosses the x-axis, _ specifies as a root

an x-value adjacent to the discontinuity. This is

reasonable because a large change in the

function value between two adjacent values of

x might be the result of a very rapid,

continuous transition. Because this cannot be

resolved by the algorithm, the root is displayed

for you to interpret.

A function may have a pole, where its

magnitude approaches infinity. If the function

value changes sign at a pole, the corresponding

value of x looks like a possible root of your

equation, just as it would for any other

discontinuity crossing the x-axis. However, for

such functions, the function value placed into

the Z-register when that root is found will be

relatively large. If the pole occurs at a value of

x that is exactly represented with 10 digits, the

subroutine may try that value and halt prematurely with an error indication.

In this case, the _ operation will not be completed. Of course, this

may be avoided by the prudent use of a conditional statement in your

subroutine.

Example: In her analysis of the stresses in a

structural component, design consultant Lucy

I. Beame has determined that the shear stress

can be expressed as

















1410for1000

100for350453

xxx

where Q is the shear stress in newtons per

square meter and x is the distance from one end in meters. Write a

subroutine to compute the shear stress for any value of x. Use _ to

find the location of zero shear stress.

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HP 15C Manuale Utente Pagina 227

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