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Shape and Space
Statistics and Probability
Two shapes are congruent if they are the same (shape and size)- in other words, if the lengths of the sides and the angles are the same.
It is often useful to know when two triangles are congruent.
Congruency and Transformations
See also: transformations.
If a shape is translated, rotated or reflected, what we are left with will be congruent to what we started with. This is because a translation just moves a shape: it doesn't change the angles or the lengths of the sides. The same is true of a rotation. A reflection might change how a shape looks, but it doesn't change the lengths of any of the sides or the size of the angles.