Thursday 20 February 2014

MFM2P - Day 13

Day 13
We spiralled back today and looked at similar triangles again.  I really wanted them to have a full example for similar triangles in their comp books so I quickly made one up for them to cut and glue.

They did pretty well matching up the angles and I heard some conversations about "scale factor" (yay!).  

Then we continued with trig. They started to have trouble when they realized that they couldn't just do the same thing for every question. They were okay with the difference between finding the length of a side and finding the measure of an angle, but solving for different sides caused problems. Their algebra skills, for the most part, are so weak that they don't have a foundation on which to develop understanding for these questions. They follow when solving an equation like:
and seem to understand why we are multiplying both sides by the denominator. However, when the variable is in the denominator like:
they have no tools to work with. I went over a case with just numbers with them... 14 divided by what gives 7? How could we write this another way? But they had a hard time transferring that to the example shown above. And they just want to memorize what to do if the variable is in the numerator and what to do if the variable is in the denominator. Sigh. I will see if I can figure out a way to better help them tomorrow...


  1. Hi Mary,
    When x is denominator, do you think Ss would get it if they approach it like other problem? Since they got the multiply both sides by 12 to "get rid" of 12th, multiply both sides by x to "get rid" of xth, next step is then more obvious. 14 = 0,7071x. Maybe that's what you did ? Admiring from afar what you and Alex are doing.

    1. Thanks for your comment, Helene. They have a lot of trouble generalizing as they have done very little work with algebra on their way to this class. I will keep plugging away! Nice to know that someone is reading my blog!