What is an Oval ? ( was Re: Newbie: Machining an oval?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "gglines1" <gglines@c...>
wrote:

>
> Where did you find those mathemtical relationships? I've found
> references to drawing them by hand using a string anchored to two
> points, but nothing about how to calculate the relationships.
>
> George

George,

You calculate point on a circle at a given angle by...

X = R * cos(angle)
Y = R * sin(angle)

For an ellipse, use half the long length for the R in the X calc and
half the short width for the R in the Y calc...

X = (length/2) * cos(angle)
Y = (width/2) * sin(angle)


In IBasic...

DEF win:WINDOW
WINDOW win, 200, 50, 400, 400, @caption, 0, "120 Segment Ellipse",
main

deg2rad=(4*atan(1))/180 : 'trig functions require angles in radians

DIAX=220 : 'long length
DIAY=90 : 'short length
XC=130 : 'X center
YC=130 : 'Y center

R1=DIAX/2 : R2=DIAY/2

FOR Ang=0 to 360 #3
if Ang>0
oldx=x : oldy=y
endif

x = R1 * cos(Ang*deg2rad)
y = R2 * sin(Ang*deg2rad)

'draw segment
if Ang>0
line win, XC+oldx, YC+oldy, XC+x, YC+y
endif
NEXT Ang

run = 1: WAITUNTIL run = 0: CLOSEWINDOW win: END

SUB main
SELECT @CLASS
CASE @IDCLOSEWINDOW
run = 0
ENDSELECT
RETURN