Are you sure you took "arcsec" rather than "arcsin" or "arccos"? The sine and cosine values are always between -1 and 1 so arcsin(2) or arccos(2) do not exist (though I can't imagine why "arcsin(1)" or "arccos(1)" would be a problem) but since secant is "1 over cosine" arcsec(2) is the same as arccos(1/2) which is and, of course, arcsec(1) is the same as arccos(1) which is 0.