Construct an isosceles trapezium and study its properties

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  • Estimated Time: 40 minutes.
  • Materials/ Resources needed: Laptop, geogebra file, projector and a pointer.
  • Prerequisites/Instructions, if any
  1. The students should know the concepts of parallel lines, perpendicular lines and rectangle.
  2. They should know basic constructions like parallel lines and perpendicular lines.
  • Multimedia resources: Laptop.
  • Website interactives/ links/ / Geogebra Applets : This geogebra file has been done by ITfC-Edu-Team
  • Process:
  1. Recall the figure trapezium and its properties.
  2. State that a trapezium with two non- parallel sides equal is an isosceles trapezium.
  3. By moving the vertices of the trapezium, you can observe trapeziums of different sizes and shapes.
  4. Make sure you note when your trapezium turns into a rectangle.
  5. Observe the symmetry of an isosceles trapezium.
  6. Study its properties.
  7. Drag the vertices of the trapezium and observe your angle measures.
  8. Make a conjecture about the base angles of an isosceles trapezium. (Both of the parallel sides are considered bases, so a trapezium has two pairs of base angles.)
  • Developmental Questions:
  1. What are parallel lines ?
  2. What is a trapezium ?
  3. Is trapezium a quadrilateral ?
  4. What are the characteristic properties of a trapezium ?
  5. What do you notice about the non-parallel sides ?
  6. How many interior angles do you see ?
  7. What is the sum of 4 angles of any quadrilateral ?
  8. What can you conclude about interior angles ?
  9. What is special about diagnols in an isosceles trapezium ?
  • Evaluation:
  1. Are all trapeziums isosceles ?
  2. Are all trapeziums quadrilaterals too ?
  3. Can rectangle be considered as an isosceles trapezium ?
  • Question Corner:

  1. State the properties of isosceles trapezium ?