Reflection: Student Ownership 2 Triangles in 1 - Section 3: More Explorations (MP 3 and MP 8)


In class notes today, students had an opportunity to lead the discussions how to use proportionality of sides in a triangle to show that lines are parallel.  After we discussed how to set-up this example, Student Work Verifying Parallel Lines, I asked the class to brainstorm with a partner ways to show that two ratios did indeed form a proportion. 

After a few minutes I selected two students to show the class two different ways.  One student proved the ratios were a proportion, by dividing each ratio and showing they had the same scale factor, while another student showed equivalent products from cross multiplying.   It was great to have them up at the front of the board discussing algebra, geometry and giving the class their own tips on how and why each method worked.

Further, when I walked around the room, I found that there really was a 50/50 split between who was using each method.  I this turned out to be a great way to differentiate instruction while at the same time giving students a voice in the class.

  Student Ownership: Student Led Problem Solving
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2 Triangles in 1

Unit 10: Sweet Similar Shapes
Lesson 4 of 8

Objective: SWBAT prove that a line parallel to one side of a triangle divides the other two proportionally while using AA criterion.

Big Idea: Students will complete a discovery activity to uncover key properties of similar triangles and apply knowledge of AA criterion.

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