This program orbits a θ character on a elliptical path. Use the arrow keys to change the size and the elliptical path. The program executes until ENTER is pressed.

Controls:

Left: Decrease of horizontal semi-axis

Right: Increase of horizontal semi-axis

Up: Increase of vertical semi-axis

Down: Decrease of vertical semi-axis

ENTER: Exits the program**HP Prime**

EXPORT ORBIT( )

BEGIN

LOCAL A,B,K,I,X,Y;

// Initialize

A:=25; B:=25; I:=0;

HAngle:=0; // Radians

X:=160+A*COS(I);

Y:=120-B*SIN(I);

MSGBOX("Press Enter to exit.");

RECT( );

REPEAT

// clear old placements and text

RECT_P(X,Y,X+10,Y+12);

RECT_P(0,218,319,239);

// get input from keyboard

K:=GETKEY;

// Adjust A and B

IF K==7 AND A>1 THEN

A:=A+1; END;

IF K==8 AND A<50 THEN

A:=A-1; END;

IF K==2 AND B<50 THEN

B:=B+1; END;

IF K==12 AND B>1 THEN

B:=B-1; END;

// Move the satellite

I:=I+π/64;

X:=160+A*COS(I);

Y:=120-B*SIN(I);

TEXTOUT_P("θ",X,Y,2);

TEXTOUT_P("A = "+STRING(A)+", B = "+STRING(B),

0,2,#FFh);

WAIT(0.05);

UNTIL K==30;

END; **TI-84 Color Plus Silver Edition**

Note: Pixels on the newer Color edition (size 250 × 150 approximately for the graph screen) opposed to the classic black and white TI-84+ (62 × 94)

Program: ORBIT

: ZStandard

: ZSquare

: FnOff

: Radian

: 5 → A

: 5 → B

: 0 → I

: ClrDraw

: AxesOff

: Repeat K=105

: Pt-Off(A cos(I), B sin(I), 2

: Text(150,0," " // 32 spaces - there is no box command

: GETKEY→ K

: If K=24 and A>1

: A-1 → A

: If K=26 and A<10

: A+1→ A

: If K=25 and B<10

: B+1→ B

: If K=34 and B>1

: B-1 → B

: I + π/16 → I

: Pt-On(A cos(I), B sin(I), 2

: Text(150,0,"A =",A,",B =",B

: End

: AxesOn

This blog is property of Edward Shore. 2014