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What one transformation is the same as a reflection over two parallel lines?

Published in Geometry 2 mins read

A reflection over two parallel lines is the same as a translation.

Understanding the Concept

Imagine two parallel lines, 'l' and 'm', and a point 'P' located between them. When you reflect 'P' over 'l', you get a point 'P1' on the other side of 'l'. Now, reflecting 'P1' over 'm' gives you a point 'P2' on the other side of 'm'.

Notice that 'P2' is simply a shifted version of 'P' by a distance equal to twice the distance between the parallel lines. This shift, or movement of a point without changing its orientation, is what defines a translation.

Example

  • Let's say the distance between the parallel lines is 5 units.
  • Reflecting a point over the first line moves it 5 units to the other side.
  • Reflecting it again over the second line moves it another 5 units.
  • The final position of the point is 10 units away from its original position, demonstrating a translation.

Conclusion

Therefore, reflecting a point over two parallel lines is equivalent to translating the point by a distance equal to twice the distance between the lines.

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