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Geometry > The Involute of a square and other shapes

Learning outcome:
  • I can trace and name the locus of a string end as it unwinds from a plane geometric figure i.e. involute.

By the end of the lesson I will be able to:

  • Draw one revolution of an involute
  • Draw a part revolution of an involute (or a combination of)
  • Design my own shapes using the involutes

Before studying this lesson I need to make sure that I know how to:

  • Draw a radial lines
  • Draw a neat freehand curve

involute of a square

The Involute of a square

An Involute is the locus of a point of a string as it unwinds from a square. This involute is drawn using compasses To see an example of this you can visit:

Note that the line forming the involute is the green one as it is the one that lies on the end of the string.

Download the involute of a square PDF version

Download the involute of other shapes PDF excercises