REM Start of BASIC! Program

FN.DEF rotate(x,y,adeg,x0,y0,resx,resy)
 LET a=TORADIANS(adeg)
 LET resx=(x-x0)*COS(a)- (y-y0)*SIN(a)+ x0
 LET resy=(x-x0)*SIN(a)+ (y-y0)*COS(a)+ y0
FN.END

!test
GR.OPEN 255,255,255,255,0,1
PAUSE 500
GR.SCREEN sx,sy

GR.COLOR 255,0,0,0,1

!the point to rotate
x=sx/10*8
y=sy/2

!the centre of rotation
x0=sx/2
y0=sy/2

DO
 FOR i=0 TO 360

  !the angle to rotate
  adeg=i

  rotate(x,y,adeg,x0,y0,&resx,&resy)

  GR.LINE vd,x0,y0,resx,resy
  GR.RENDER

 NEXT i

 PAUSE 1000
 GR.CLS
 x0=sx/10*2+int(rnd()*sx/10*6)
 y0=sy/10*2+int(rnd()*sy/10*6)

UNTIL 0