Perimeter of the Ellipse (HP-15C)

[Gerson W. Barbosa]

Another method (under test)

p ~ π(a - b)(y + 1/(4y - 1/(4y - 3/(4y - 3/(4y - 4/(4y))))))

where

y = (a + b)/(a - b)

HP-75C, HP-71B program:

Code:


10 OPTION BASE 1
15 DIM N(5) 
20 INPUT A,B
25 IF A=B THEN B=-B @ Y=1 @ C=0 @ GOTO 65
30 Y=(A+B)/(A-B)
35 D=4*Y
40 C=0
45 FOR I=1 TO 5
50 READ N(I)
55 C=N(I)/(D-C)
60 NEXT I
65 P=PI*(A-B)*(Y+C)
70 DISP P
75 END
99 DATA 4,3,3,1,1

An HP-15C version could be slightly more accurate and perhaps faster than my first program.