Canvas ArcTo confusion

So I am once again dealing with annular sectors which is not my forte. I can use the .arc method on canvas just fine, the problem comes from needing my arc to be part of a path.

So for example:

 ctx.save();
 ctx.arc(centerX, centerY, radius, startAngle, endAngle, true);
 ctx.stroke();
 ctx.restore();

Works fine. But now I need it as part of a path, so I have something like this:

 var pointArray = [...]; //this contains all four corner points of the annular sector
 ctx.save();
 ctx.moveTo(pointArray[0].x, pointArray[0].y);
 ctx.lineTo(pointArray[1].x, pointArray[1].y); //so that draws one of the flat ends
 ctx.arcTo(?, ?, pointArray[2].x pointArray[2].y, radius);

That tangent of tangent coordinate is driving me mad. Plus I have a serious concern: http://www.dbp-consulting.com/tutorials/canvas/CanvasArcTo.html Makes it sound like an arc drawn with arcTo could never cover 180degrees or more of a circle and there will be times that my annular sector will be greater than 180degrees.

Thanks for the help superior geometric minds of stackoverflow!

UPDATE Ok, so I am having to do svg canvas inter-polarity here, and using coffee-script, actual production code follows!

 annularSector : (startAngle,endAngle,innerRadius,outerRadius) ->

    startAngle  = degreesToRadians startAngle+180
    endAngle    = degreesToRadians endAngle+180
    p           = [ 
        [ @centerX+innerRadius*Math.cos(startAngle),    @centerY+innerRadius*Math.sin(startAngle) ]
        [ @centerX+outerRadius*Math.cos(startAngle),    @centerY+outerRadius*Math.sin(startAngle) ]
        [ @centerX+outerRadius*Math.cos(endAngle),      @centerY+outerRadius*Math.sin(endAngle) ]
        [ @centerX+innerRadius*Math.cos(endAngle),      @centerY+innerRadius*Math.sin(endAngle) ] 
    ]
    angleDiff   = endAngle - startAngle
    largeArc    = (if (angleDiff % (Math.PI * 2)) > Math.PI then 1 else 0)

    if @isSVG

        commands    = []

        commands.push "M" + p[0].join()
        commands.push "L" + p[1].join()
        commands.push "A" + [ outerRadius, outerRadius ].join() + " 0 " + largeArc + " 1 " + p[2].join()
        commands.push "L" + p[3].join()
        commands.push "A" + [ innerRadius, innerRadius ].join() + " 0 " + largeArc + " 0 " + p[0].join()
        commands.push "z"

        return commands.join(" ")

    else

        @gaugeCTX.moveTo p[0][0], p[0][1]
        @gaugeCTX.lineTo p[1][0], p[1][1]
        #@gaugeCTX.arcTo 
        @gaugeCTX.arc @centerX, @centerY, outerRadius, startAngle, endAngle, false
        #@gaugeCTX.moveTo p[2][0], p[2][1]
        @gaugeCTX.lineTo p[3][0], p[3][1]
        @gaugeCTX.arc @centerX, @centerY, innerRadius, startAngle, endAngle, false          

THE SOLUTION

        @gaugeCTX.moveTo p[0][0], p[0][1]
        @gaugeCTX.lineTo p[1][0], p[1][1]
        @gaugeCTX.arc @centerX, @centerY, outerRadius, startAngle, endAngle, false
        @gaugeCTX.lineTo p[3][0], p[3][1]
        @gaugeCTX.arc @centerX, @centerY, innerRadius, endAngle, startAngle, true #note that this arc is set to true and endAngle and startAngle are reversed!