Mirror Images — Prelims Strategy

Prelims Strategy

Locate the mirror line first and identify two features that are not symmetric about it. A corner dot and an arrowhead often provide a stronger test than the outline alone. For a vertical line, retain each feature's height and reverse its perpendicular placement. Compare candidates against those constraints before considering less distinctive decoration.

Use coordinates if the line is displaced from the origin. A point's image across x = a lies at x = 2a - x, with y unchanged. Merely changing the sign of x assumes a mirror at zero. For a row of figures, check both reversed order and the internal reflection of each figure; one correct reversal does not compensate for an unchanged asymmetric symbol.

Reject half-turn distractors by following a point above the horizontal axis: a vertical reflection keeps it above, while the half-turn moves it below. Finish by reflecting the candidate back across the same line. It should restore the original exactly. If the question uses letters, rely on the drawn glyph rather than assume all typefaces have identical symmetry.