Teaching Geometry - Law of Cosines #VNPS

Next up was Law of Cosines.  I decided we did a lot of discovering lately and from teaching Law of Cosines in Algebra 2, I know they really struggle with the calculator buttons.  So, I gave them the Law of Cosines.  I asked them to write it down on the board and then to write down things they notice:



I gave them an example with side, side, side and asked them to find the largest angle first.  I asked them to undo all the algebra first and write it on the board, only picking up the calculator at the last step.

This was one mistake, finishing as the cosC is 81.4 instead of just m<C is 81.4.  We talked about that.  They keep telling themselves, when you don't have the angle, you have to use the inverse button.



Then, this student continued with the same problem and wanted to switch over the Law of Sines to finish.



I followed this with a side, angle, side example.



Law of Cosines Lesson PPT
Law of Cosines Lesson Board Problems

We did not do the bearings at the board.  I had them come back to their desks and notes and directly taught it.