HP 15c - Manual (Page 24)

24 Section 1: Using _ Effectively
24
Based on these samples, try using an extreme estimate of −0.25 and initial _
estimates (in radians ) near 10° and 30°.
Keystrokes Display
.25 ”O9 -0.2500 Stores extreme estimate.
.2
v 0.2000
.6 0.6 Initial estimates.
´_1 Error 8 No root found.
−O4 0.4849 Stores θ estimate.
)O5 0.4698 Stores previous θ estimate.
) 0.0457 Distance from extreme.
.9
* 0.0411 Revises extreme estimate
by 90 percent of the distance.
O+9 0.0411
l4 0.4849 Recalls θ estimate.
vv´B -0.2043 Calculates intensity E.
− 0.0000 Recalls other θ estimate,
keeping first estimate in Y-
register.
l5 0.4698
´_1 Error 8 No root found.
− 0.4898 θ estimate.
® 0.4893 Previous θ estimate.
® 0.4898 Recalls θ estimate.
vv´B -0.2043 Calculates intensity E.
® 0.4898 Recalls θ value.
|d 28.0660 Angle in degrees.
|D 28.0660 Restores Degrees mode.
The second interaction produces two θ estimates that differ in the fourth decimal place. The
field intensities E for the two iterations are equal to four decimal places. Stopping at this
point, a minimum field intensity of −0.2043 is indicated at an angle of 28.0660°. (This angle
differs from the previous solutions by about 0.002°.)
Applications
The following applications illustrate how you can use _ to simplify a calculation that
would normally be difficult—finding an interest rate that can't be calculated directly. Other
applications that use the _ function are given in Sections 3 and 4.
Annuities and Compound Amounts
This program solves a variety of financial problems involving money, time, and interest. For
these problems, you normally know the values of three or four of the following variables and
need to find the value of another: