Similarity

Lesson Plan on Similarity of triangles drawn by Ms. Lakshmidevi Nair a teacher trainee at Pushpanjali College of Education, Vasai, India

Approach used: 5 E Approach

Engage: All students were given a geometrical figure each. They group themselves and explain on what basis they formed a group. In this case, all circles were grouped together. All triangles formed one group and so on.the teacher told them they had used the principle of similarity.
Explore: The teacher had the class arranged in groups of 5 to 6 students. Each group had a worksheet with two triangles. the teacher told them the traingles were similar and that the class would find the properties of similar triangles. The group had to find the lengths of the sides and measures of the angles. Next they found the ratio of the corresponding sides. The groups compared their findings and came to some conclusions.
Explain: The students explained the conclusions drawn. They discovered for themselves that similar triangles have corresponding sides that are proportional.
Elaborate: The teacher asked the class to furnish examples where the principles of similarity are used. Students gave examples of how maps are drawn to scale, how architects use the principles of similarity when preparing a blueprint of a building.
Evaluate: The teacher provided an example where the triangles are similar and the students had to find the lengths of the sides given the required information.
The lesson was truly constructivist in approach as all properties were derived by the students themselves.The activity during the 'elaborate' stage helped to see the application of what was being learnt.Co-operative learning ensured participation of all.