Wednesday, January 15, 2014

Triangle Congruences Lesson

I have been struggling to find a lesson plan for teaching SSS, SAS, ASA & AAS for about a week.  I have been teaching geometry about 12 of my 14 years and have yet to find a lesson that I truly love, that my students buy into easily.  Early in my career, I went straight by the (text) book.  As a teacher that likes to use manipulatives, I have used straws and chenille stems to have them "discover" which of the 6 abbreviations actually worked every time.  That lesson works with certain kids and I didn't feel that this year's students would like it.  It seems every year the students get more and more resistant to reading and following instructions step-by-step!

So, as a seasoned procrastinator, I designed today's lesson last night, printed it out, revamp, printed again, then photocopied before school this morning on my famous colored paper.  I don't want to get too excited, but they seemed to like it and did well identifying all 6 shortcuts (including SSA and AAA).

Here's how the class period rolled.  As the students walked in, I told them to pick up one of each sheet. After attendance, I briefly explained congruent triangles and how they could be congruent by SASASA, but that we only needed 3 letters.  I let them tell me the 6 combinations.  I drew pics of 2 triangles for each, showing the appropriate tick marks.  At this point, I told them to cut out the 10 squares and place them on the other half sheet in the correct column.  As they worked, I walked around checking answers and moving the incorrect ones for them to try again.  Some had a couple wrong, some didn't even have but a couple correct.  For those, I explained one or two and they were able to get the rest correct.  If I gave them the go-ahead, they glued the squares down, then glued/taped the activity into their INB.


This activity can be found at my TPT store.


















After everyone was done, I explained that 2 of the shortcuts (SSA and AAA) were not guarantees that the triangles were congruent and that if something doesn't work every time, we don't use it in math. The next activity was a worksheet with 2 congruent triangles for each problem.  They had to identify the shortcut and the name of the triangle that was congruent to the first one.  The letters of the triangles were written at the bottom to complete a statement.  It is an awesome self-checking worksheet that I found at Math Teacher Mambo's blog and my kids really enjoyed it.


2 comments:

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