pro arc,centre,radius,angle,noerase=noerase, $
axes=axes,color=color,a_color=a_color,linestyle=linestyle, $
a_linestyle=a_linestyle,thick=thick

;	Draws an arc in a graphic device.

angle0=angle+360

if n_elements(noerase) le 0 then noerase=0
if n_elements(color) le 0 then color=!p.color
if n_elements(thick) le 0 then thick=1
if n_elements(a_color) le 0 then a_color=!p.color
if n_elements(linestyle) le 0 then linestyle=!p.linestyle
if n_elements(a_linestyle) le 0 then a_linestyle=!p.linestyle

t=findgen(1080)*!pi/180

x=cos(t)*radius+centre(0)
y=sin(t)*radius+centre(1)
x0=float(centre(0)-radius)/!d.x_vsize
x1=float(centre(0)+radius)/!d.x_vsize
y0=float(centre(1)-radius)/!d.y_vsize
y1=float(centre(1)+radius)/!d.y_vsize

plot,x,y,xst=5,yst=5,pos=[x0,y0,x1,y1]*0.9999,noerase=noerase,/nodata

oplot,x(angle0(0):angle0(1)),y(angle0(0):angle0(1)), $
	color=color,linestyle=linestyle,thick=thick


	if keyword_set(axes) then begin
xc=float(centre(0))/!d.x_vsize
yc=float(centre(1))/!d.y_vsize
plots,[xc,xc],[0,1],/nor,color=a_color,linestyle=a_linestyle
plots,[0,1],[yc,yc],/nor,color=a_color,linestyle=a_linestyle

	endif


end