To see the full height of man, the height of mirror should be half of the height of the man. What happens when we decrease the distance between mirror and man?
It does not matter where the mirror is kept for you to see the entire image. A mirror with half the length of the man should be sufficient irrespective of the position. The only thing you do have to make sure is that when the mirror is brought closer, it must not be moved vertically. This can be understood from the following diagram:-
The rectangle is the person and the two black strips are mirrors. The lines depict the rays which come from the extremities of the person, and hence if these rays reach to the eyes, the person can see his entire image.The point where the rays converge, is the level of the eye, exaggerated to allow for easy spacing.