# Construct an isosceles trapezium and study its properties

From Karnataka Open Educational Resources

- Estimated Time: 40 minutes.
- Materials/ Resources needed: Laptop, geogebra file, projector and a pointer.
- Prerequisites/Instructions, if any

- The students should know the concepts of parallel lines, perpendicular lines and rectangle.
- 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:

- Recall the figure trapezium and its properties.
- State that a trapezium with two non- parallel sides equal is an isosceles trapezium.
- By moving the vertices of the trapezium, you can observe trapeziums of different sizes and shapes.
- Make sure you note when your trapezium turns into a rectangle.
- Observe the symmetry of an isosceles trapezium.
- Study its properties.
- Drag the vertices of the trapezium and observe your angle measures.
- 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:

- What are parallel lines ?
- What is a trapezium ?
- Is trapezium a quadrilateral ?
- What are the characteristic properties of a trapezium ?
- What do you notice about the non-parallel sides ?
- How many interior angles do you see ?
- What is the sum of 4 angles of any quadrilateral ?
- What can you conclude about interior angles ?
- What is special about diagnols in an isosceles trapezium ?

- Evaluation:

- Are all trapeziums isosceles ?
- Are all trapeziums quadrilaterals too ?
- Can rectangle be considered as an isosceles trapezium ?

- Question Corner:

- State the properties of isosceles trapezium ?