Marking the intersecting area between two circles in Canvas

I am trying to mark the overlapping area between two circles (like in a Venn Diagram). I figured the way to do this is by drawing two arcs using the two intersecting points and than fill the path using fill(). I know the coordinates of the intersection points, but how do I use that as an input for the arc() function?

ctx.beginPath();
ctx.arc(circle1.x,circle1.y,circle1.r, ? , ? ,true);
ctx.fill();
ctx.closePath();