HP 15c - Manual (Page 14)

14 Section 1: Using _ Effectively
14
First convert 5° 18'S to decimal degrees (press 5.18”|À), obtaining −5.3000
(using •4 display mode). (Southern latitudes are expressed as negative numbers for
calculation purposes.)
The solution to Coulerre's problems is the value of t satisfying
−5.3000 = a
4
t
4
+ a
3
t
3
+ a
2
t
2
+ a
1
t + a
0
.
Expressed in the form required by _ the equation is
0 = a
4
t
4
+ a
3
t
3
+ a
2
t
2
+ a
1
t − 2.8806
where the last, constant term now incorporates the value of the declination.
Using Horner's method, the function to be set equal to zero is
f(t) = (((a
4
t + a
3
)t + a
2
)t + a
1
)t − 2.8806 .
To shorten the subroutine, store and recall the constants using the registers corresponding to
the exponent of t.
Keystrokes Display
= - PrError Clears calculator’s memory. *
− 0.0000
|¥ 000- Program mode.
´bA 001-42,21,11
l4 002- 45 4
* 003- 20
l3 004- 45 3
+ 005- 40
* 006- 20
l2 007- 45 2
+ 008- 40
* 009- 20
l1 010- 45 1
+ 011- 40
* 012- 20
l 0 013- 45 0
+ 014- 40
|n 015- 43 32
* This step is included here only to ensure that sufficient memory is available for the examples that follow in this handbook.