MathematicsExam code: 0580

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Mirror lines

  • A line of symmetry is a line across a shape such that folding along it makes the two halves match exactly
  • Each half is the mirror image of the other, so a shape can be completed from half of it and the line
  • Diagonal lines of symmetry are easy to miss, and turning the page helps
  • You may use tracing paper in the examination, and it is the quickest way to test a line you are unsure of
  • Questions ask you to draw all the lines of symmetry or to shade squares to make a pattern symmetrical, so check horizontal, vertical and both diagonals every time
    • A rectangle has 2, a square has 4, and a regular polygon with n sides has n
A cross-shaped tile made of shaded and unshaded squares with all four of its lines of symmetry drawn dashed: one vertical, one horizontal and both diagonals through the centre
Source: Lines of symmetry by Save My Exams
Lines of symmetry drawn as dashed lines: one down an isosceles triangle, four on a square through both pairs of opposite sides and both diagonals, and two on a rectangle, with the reminder that a rectangle's diagonal is not a line of symmetry because the halves do not fold onto each other
Source: Lines of symmetry by Save My Exams

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