Trig Introduction

Today in grade 10 applied, we introduced trigonometry and reviewed our measurement skills.

The sequence of the task was as follows: Everyone needs to draw a right angle triangle with one angle that is 30 degrees.

We quickly noticed that students were struggling with protractors and rulers, and even the vocabulary of right angle.

I took a step back and tried to connect to prior knowledge. I cut out a triangle and labelled the angles then ripped out the angles and recombined them to form a line.

We knew that half of a circle is 180 degrees since a whole circle is 360 degrees. We know that all the angles in the triangle add up to 180 degrees. We know that our protractor also is 180 degrees. We talked about different types of angles, and different triangle words we knew, and then we got back into trying the task.

We needed quite a bit of help to make sure that our angles were accurately drawn, but eventually we got there!

Step 2 was to measure the 3rd angle.
Step 3 was to measure all of the 3 sides, using decimal numbers to be accurate.

Step 4 was to put all of the data from our triangles in the table on the whiteboard.

These triangles we made are all kind of the same, since their angles are all the same. The vocabulary of similar triangles was introduced and can be built on later.

I told the students that I’m magic and I can tell by looking at the table which triangles were perfectly accurate, and which were close, and which were not so close. I’m not sure if they believe me or not, but some wanted to try to learn my trick!

It didn’t take long for someone to notice that the long side is double the short side for the triangles that were deemed to be perfect.

We introduced new vocabulary of adjacent, opposite, and remembered hypotenuse, and then introduced the mnemonic device SOH CAH TOA

For an introductory day we covered a lot of skills, and reviewed several skills from earlier years. Looking forward to getting out the clinometers and doing some measurements next week.