A Trapezium and its properties

From Karnataka Open Educational Resources

Learning objectives

  1. A quadrangle with only two opposite sides parallel is called a trapezium, or trapezoid.
  2. The parallel sides are called the bases of the trapezium and the other two sides are called the legs or the lateral sides.
  3. If the legs are equal in length, then this is an isosceles trapezium.
  4. The distance between the bases is called height of trapezium.

Notes for teachers

Activity No # 1. Properties of a trapezium.

  • Estimated Time :40 minutes.
  • Materials/ Resources needed:

Laptop, geogebra file, projector and a pointer.

  • Prerequisites/Instructions, if any
  1. Knowledge about parallel lines, angles and diagnols.
  • Multimedia resources: Laptop.
  • Website interactives/ links/ / Geogebra Applets: This file has been taken from www.geogebratube.org

  • Process:
  1. Show the geogebra file and explain its properties by asking the questions listed below.
  • Developmental Questions:
  1. What is a trapezium ?
  2. How many sides does it have ?
  3. What can be said about the pair of sides ?
  4. Identify the diagnols. Are they equal ?
  5. What would be the sum of 4 angles of the trapezium ? Why so ?
  6. What would be the sum of its two allied angles ?
  7. Are the two pairs of sides of a trapezium equal ?
  • Evaluation:

Are the students able to apply the theorems of parallel lines - transversal to prove the properties.

  1. Why are allied angles of the trapezium supplementary ?
  2. Are the diagnols equal ?
  3. Is trapezium a parallelogram ?
  • Question Corner:
  1. List the properties of a trapezium.
  2. What properties of other quadrilaterals does it share. Compare with other quadrilaterals.