HP 15C: Coordinates
on an Ellipse
Store the following values before running:
R0 = number of points.
θ always starts at 0° to 360° in equal increments.
R1 = a, length of horizontal semiaxis
R2 = b, length of vertical semiaxis
R3 is used as a counter.
The center is assumed to be (0,0).
Program:
Step

Key

Key Code

001

LBL B

42, 21, 12

002

DEG (Degrees mode)

43, 7

003

RCL 0

45, 0

004

1

1

005



30

006

3

3

007

10^X

13

008

÷

10

009

STO 3

44, 3

010

3

3

011

6

6

012

0

0

013

RCL÷ 0

45, 10, 0

014

STO 4

44 ,4

015

LBL 2

42, 21, 2

016

RCL 3

45, 3

017

INT

43, 44

018

R/S

31

019

RCL* 4

45, 20, 4

020

ENTER

36

021

COS

24

022

RCL* 1

45, 20, 1

023

R/S

31

024

X<>Y

34

025

SIN

23

026

RCL* 2

45, 20, 2

027

R/S

31

028

ISG 3

42, 6, 3

029

GTO 2

22, 2

030

RTN

43, 32

Outputs:
Point number (0 through n1), [ R/S ]
X coordinate [ R/S ],
Y coordinate [ R/S ]
The program continues until all the points are revealed.
Example:
R0 = 6, R1 =
1.2500, R2 = 2.4700 (FIX 4 mode)
Point #

X

Y

0

1.2500

0.0000

1

0.6250

2.1391

2

0.6250

2.1391

3

1.2500

0.0000

4

0.6250

2.1391

5

0.6250

2.1391

how to check coordinates of ellipse
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