Thank you for your response. I see where you are coming from. I think because I don't interpret their text as saying that i is "half of -1" but "half of the rot

Thank you for your response. I see where you are coming from. I think because I don't interpret their text as saying that i is "half of -1" but "half of the rotation that would lead to -1" I consider your description equivalent. In fact I am struggling to interpret their text to say "half of -1". Regardless, I see your point.