“…= ((a + f (y 0 ) cos(bx) − g(y 0 ) sin(bx)) cosh x, f (y 0 ) sin(bx) + g(y 0 ) cos(bx), (a + f (y 0 ) cos(bx) − g(y 0 ) sin(bx)) sinh x), 2 and hence, the meridian is always timelike. So, for the cases of our "surface is timelike, loxodrome is spacelike, meridian is timelike" and "surface is timelike, loxodrome is timelike, meridian is timelike" we can take b = 0; but for the case of our "surface is spacelike, loxodrome is spacelike, meridian is spacelike", "surface is timelike, loxodrome is spacelike, meridian is spacelike" and "surface is timelike, loxodrome is timelike, meridian is spacelike" we cannot take b = 0.…”