Drag on the sphere

There are two kinds of drag that are defined.  One is "skin drag" which is the integral of the tangential force on the surface of the sphere. This is defined to be 0 for inviscid fluids.  The "form drag" is the integral of the total normal stress over the entire sphere.  Because the pressure is the only normal stress for an inviscid fluid, we can guess that the form drag is likewise 0 because the picture is clearly symmetric.   

Let's calculate the form drag anyway.   See Denn page 253 for the low Re case.