## Lines and planes of Symmetry

If you take a sheet of A4 paper and fold it in half, both halves will look exactly the same. We call the fold you just made a ‘line of symmetry’.

So in 2D shapes you get a line of symmetry, and the lines are 1D.

In 3D shapes, instead you get a plane of symmetry, which is a 2D area.

Like a line of symmetry, on either side of the plane of symmetry, the shape is identical.

To identify the reflection symmetry of 3D shapes it is useful to first imagine where those planes should be.

A useful tip to do this is for each side of the 3d shape see if there is a line of symmetry. If there are any; if you cut straight through the shape in that line, would you get two identical halves (practically a reflection)?

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