**HP 42S Programming Part II: Dew Point, Ellipse Area and Eccentricity, Easy Transverse**

Click here for Part I: Matrix Column Sum, GCD, Error Function

(I plan to post Part III next week.)

As mentioned in Part I, you can download an emulator for the HP 42S, Free42 here: http://thomasokken.com/free42/ . The emulator is for many operating systems including Windows, Mac, iOS, and Android.

**HP 42S: Dew Point (°C)**

00 {99-Byte Prgm}

01 LBL “DEW”

02 “TEMP °C:”

03 PROMPT

04 STO “T”

05 “HUMIDITY %”

06 PROMPT

07 STO “H”

08 LN

09 17.27

10 RCL* “T”

11 237.3

12 RCL+ “T”

13 ÷

14 +

15 17.27

16 ÷

17 STO “V”

18 237.3

19 RCL* “V”

20 1

21 RCL- “V”

22 ÷

23 “DEW POINT °C”

24 ARCL ST X

25 AVIEW

26 STOP

27 END

Instructions: Execute
GTO DEW from Home. Press [R/S].

Test: Input: T:
20°C, H = 0.50

Result: 9.2696°C

HP 42S: Area and
Eccentricity of an Ellipse

The program ELLIPSE calculates the area and eccentricity of
an ellipse.

Formulas:

Assume a>b, where a and b represent the lengths of
semi-diameters, respectively

Area: A = π*a*b

Eccentricity: ϵ =
√(1 – (b/a)^2)

00 {76-Byte Prgm}

01 LBL “ELLIPSE”

02 “LARGE S-D:” \\
S-D: semi-diameter

03 PROMPT

04 STO “A”

05 “SMALL S-D:”

06 PROMPT

07 STO “B”

08 RCL “A”

09 RCL* “B”

10 PI \\ π

11 *

12 “AREA:”

13 AVIEW

14 PSE

15 STOP \\ R/S

16 1

17 RCL “B”

18 RCL÷ “A”

19 X^2

20 –

21 SQRT

22 “ECC:”

23 AVIEW

24 PSE

25 END

HP 42S Easy Transverse

Calculates the new point knowing the original
coordinates, direction, and angle of travel. The angle 0° comes from due
east and rotates counterclockwise. The
program sets the HP 42S to degrees mode.
We make use of the Programmable Menu.

00 {183-Byte Prgm}

01 LBL “EASYTRV”

02 DEG

03 0

04 STO “T” \\
initialize total distance counter

05 “INITIAL EASTING”

06 PROMPT

07 STO “E”

08 “INIT. NORTHING”

09 PROMPT

10 STO “N”

11 LBL 00 \\ main label

12 XEQ 01 \\ go to calculation sub loop

13 LBL 03 \\ start menu label

14 CLMENU

15 “NEXT”

16 KEY 1 XEQ 01 \\ KEYX command

17 “QUIT”

18 KEY 2 GTO 02 \\ KEYG command

19 MENU

20 STOP

21 GTO 03 \\ end menu loop

22 LBL 01 \\ main calculation loop

23 CLRMENU \\ make both lines available for viewing

24 “ANGLE (0°-360°)”

25 PROMPT

26 STO “A”

27 “DISTANCE”

28 PROMPT

29 STO “D”

30 STO+ “T”

31 →REC

32 STO+ “E”

33 X<>Y

34 STO+ “N”

35 RCL “E”

36 “EAST:”

37 ARCL ST X

38 AVIEW

39 STOP

40 RCL “N”

41 “NORTH:”

42 ARCL ST X

43 AVIEW

44 RTN

45 LBL 2 \\
finalization sub routine

46 CLMENU

47 RCL “T”

48 “ΣDIST:” \\ Σ is from the ALPHA-MATH menu

49 ARCL ST X

50 AVIEW

51 STOP

52 RCL “N”

53 RCL “E”

54 END

Test:

Initial Data Coordinates: N = 1,000,
E = 1,000

Travel #1: 170 units
at 118° (28° NW)

Travel #2: 162 units
at 45° (45° NE)

Input:

[XEQ] {EASYT}

1000 [R/S] [R/S]

118 [R/S] 170 [R/S]

Result:

EAST: 920.1898 [R/S],
NORTH: 1,150.1011

{NEXT} 45 [R/S] 162 [R/S]

EAST: 935.5061 [R/S],
NORTH: 1,192.4143

{QUIT} ΣDIST: 215
[R/S], N on Y stack, E on X stack.

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