Wednesday 6 May 2015

MFM2P - Day 59: Trig

Today's visual pattern asked for both the volume and surface area. They saw how the volume (number of cubes) grew, but had more trouble with the surface area. We used linking cubes to make the shapes which helped a lot. Next time I want to show them other ways of seeing it.

Next, on to trig. They have found both angles and side lengths of right angled triangles before using trig tables. Today I introduced them to SOH-CAH-TOA. I find it helpful to write it like this so that the ratios are more obvious:

Here is the handout they received. We got through example 3 together and then moved on to this. Yes! We were going to go outside! I showed them how a clinometer works.

I asked what data they would need to collect and we came up with this diagram:

I put them in random groups and told them they had 15 minutes to be back in class. Out they went (it was beautiful out) and started measuring. Some groups were finding the height of a tree, others a hydro pole and one group the light standard. They came back in the school to take measurements (as a large group) for the ramp then we all headed back to our classroom. They wrote the measurements they took for the ramp on the board for everyone to use:

And that was it. Tomorrow they will do the calculations and practice a little more trig.


  1. Not sure if you let kids use their phones in class, but there are a handful of really nice clinometer apps available that can replace the only protractor and string thingy. The good ones allow you to capture an image, with an angle measurement overlay.

  2. Thanks for the reminder! I do have a clinometer app on my phone, but was not organized enough to get the kids to download one ahead of time. Next time...