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GeoGebraGeoGebra Classroom

Similar Figures

Similar Figures Similar figures have the same shape, but can be moved somewhere else (translation), different in size (dilation), turned around (rotation), or a mirror image of the other shape (reflection). Figures can be described as similar if they meet the following conditions.
  • Their angles are congruent.
  • Their corresponding sides are in the same proportion to each other (e.g. all the same size, or all increased by a scale factor of 2).
Angles can be described as 'congruent' when they are the same and in the same order (although they could be arranged anticlockwise rather than clockwise).
Move the dots around to change the original figure, or to change the line of reflection. See what changes on the other figures and what stays the same. Check if the figures are always similar - are the sides always in the same proportions and do the angles remain congruent? What would you have to change for the figures to stop being similar? Can you do it? Can you work out what the scale factor is between the original and the dilated figures?