This program is Copyright © 1975 by HewlettPackard and is used here by permission. This program was originally published in "HP55 Mathematics Programs".
This program is supplied without representation or warranty of any kind. HewlettPackard Company and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.
If the xy coordinates of the vertices of a polygon are known, the area can be found by the following formula:
Area = 0.5 * [(x_{1} + x_{2})(y_{1}  y_{2}) + (x_{2} + x_{3})(y_{2}  y_{3}) + . . . + (x_{n} + x_{1})(y_{n}  y_{1})]
Traverse the coordinates clockwise for a positive area.
Step 
Instructions 
Input Data/Units 
Keys 
Output Data/Units 
1 
Enter program 

2 
Input (x_{1}, y_{1}) 
x_{1}* 
ENTER 

y_{1}* 
BST R/S 
0.0 

3 
Input (x_{i}, y_{i}) for i = 2, . . ., n 
x_{i} 
ENTER 



y_{i} 
R/S 
intermediate 
4 
Input (x_{1}, y_{1}) again 
x_{1} 
ENTER 



y_{1} 
R/S 
Area 

* if x_{1} & y_{1} are complicated 




you can store them in R6 and 




R7 for step 4. 



For a polygon with the points (1,3), (2,4), (5,4), (5,7) (7,5), (7,1), (3,1), the area would be 19.50.
LINE CODE KEYS 00. 01. 33 STO 02. 02 2 03. 23 roll dn 04. 33 STO 05. 01 1 06. 00 0 07. 33 STO 08. 05 5 09. 84 R/S 10. 33 STO 11. 04 4 12. 23 roll dn 13. 33 STO 14. 03 3 15. 34 RCL 16. 01 1 17. 61 + 18. 34 RCL 19. 02 2 20. 34 RCL 21. 04 4 22. 51  23. 71 x 24. 02 2 25. 81 ÷ 26. 33 STO 27. 61 + 28. 05 5 29. 34 RCL 30. 04 4 31. 33 STO 32. 02 2 33. 34 RCL 34. 03 3 35. 33 STO 36. 01 1 37. 34 RCL 38. 05 5 39. 09 GTO 09
R1 x_{i1} R2 y_{i1} R3 x_{i} R4 y_{i} R5 area
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