Casio
fx3650p and HP 21S: The Intersection
Point of a Quadrilateral
Introduction
This program calculates the coordinates of the center
of quadrilateral. For the derivation,
please see this link: http://edspi31415.blogspot.com/2017/08/geometryintersectionpointof.html
Casio
fx3650P
See the diagram below.
Due to the lack of variable available, 7, the
program asks for A, B, C, and D twice.
Most of my programs asks for the inputs, then executes
calculations. This program asks for some
inputs, does some calculations, then asks for more input, then executes calculations,
including replacing variables to make room for further calculations.
Program (91 steps):
? → A : ? → B : ? → C : ? → D :
(D – B) ÷ (C – A → X :
B – A X → Y :
? → A : ? → B : ? → C : ? → D :
(D – B) ÷ (C – A → C :
B – A C → D :
(D – Y) ÷ (X – C → X ◢
D + C X → Y
HP 21S
See the diagram below. Input the following points into R0 through
R7.
Program (the code and steps should be the same for
the HP 20S):
Step

Code

Key

01

61, 41, A

LBL A

02

33

(

03

22, 3

RCL 3

04

65



05

22, 1

RCL 1

06

34

)

07

45

÷

08

33

(

09

22, 2

RCL 2

10

65



11

22, 0

RCL 0

12

74

=

13

21, 8

RCL 8

14

55

*

15

22, 0

RCL 0

16

32

+/

17

75

+

18

22, 1

RCL 1

19

74

=

20

21, 0

STO 9

21

33

(

22

22, 7

RCL 7

23

65



24

22, 5

RCL 5

25

34

)

26

45

÷

27

33

(

28

22, 6

RCL 6

29

65



30

22, 4

RCL 4

31

34

)

32

74

=

33

21, 6

STO 6

34

55

*

35

22, 4

RCL 4

36

32

+/

37

75

+

38

22, 5

RCL 5

39

74

=

40

21, 7

STO 7

41

33

(

42

22, 7

RCL 7

43

65



44

22, 9

RCL 9

45

34

)

46

45

÷

47

33

(

48

22, 8

RCL 8

49

65



50

22, 6

RCL 6

51

74

=

52

21, 8

STO 8

53

26

R/S

54

55

*

55

22, 6

RCL 6

56

75

+

57

22, 7

RCL 7

58

74

=

59

21, 9

STO 9

60

61, 26

RTN

Variables – HP 21S:
Register

Input

Output

R0

A1


R1

B1


R2

C1


R3

D1


R4

A2


R5

B2


R6

C2

C’

R7

D2

D’

R8


X

R9


Y

Example
From topleft hand corner clockwise: (1, 4), (4, 6), (5, 1), (0, 0)
Results:
X = 1.357142857
Y = 2.035714286
Eddie
This blog is property of Edward Shore, 2017.