I think i have a clear understanding of how to calculate angular resolution in arcsec/pix.

I have attached an image of my calculation for my T3i camera and AT72ED refractor.

pixel size - 4.29 microns, FL = 430mm

What I dont undertsand is that the final output is simply arcsec. The units seem to cancel out that way. Given that the solid angle is a measure of angular size, shouldn't the units be squared? arcsec^2?

I want to ultimately solve for the entire area in arc-sec^2 visible in my camera's FOV. Should I simply square my calculation for arc-sec/pix and then apply it over the 18,000,000 pixels? Im not sure if im missing something. My math could be completely wrong. If anyone has any knowledge about this, please chime in - im at a sort of a crossroads.