Imaginary Numbers Are Real (Part 9: Closure)

The last video in a series about imaginary numbers demonstrates the need for complex numbers. Math pupils learn that they need to include the square root of negative one, the building block of the complex numbers, to have a set of numbers that are closed under all operations.

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CCSS: Adaptable
Instructional Ideas

  • Provide a more extensive discussion of closure, along with determining what sets of numbers are closed under what operation
  • Have pairs research the different subsets of the complex numbers and develop a poster to display the information they found
Classroom Considerations

  • The final video of a nine-video series
Pros

  • Video is versatile for multiple uses in your classroom
  • Applicable and illustrative resource for your lesson
Cons

  • A mistake was made in not showing that natural numbers are closed under powers
  • Closure is not specifically mentioned in the CCSS, so video goes beyond the requirements of CCSS
Common Core