This is related to the recent question on the inclusion of images of pages in questions. The answer, which in my opinion was quite reasonable, is that the question should contain enough context to be understandable (and by extension, answerable) without the external content.
Should we assume the same policy ought to apply to answers that consist of nothing but "This is proven in this book, here's an image of the page"? E.g., this example?
Edit. The answer has been edited to remove the image. Nonetheless, is the consensus also that the same standards applied to questions in this regard should extend to answers?