Proving Trig IDs

Jul 2, 2014 6:48am

One standard my students did not meet is in regards to proving a relationship between two identities true. One strategy I have used is to start with the more complicated expression and through algebraic manipulation like substitution, addition/subtraction of rational expression, and multiplying by a special value of one, and so on, they will eventually arrive at the desired expression. And if that doesn't work, I suggest to my students to work both expression. All this seems time consuming and only the students that know their algebra are successful. Besides exposing them to more practice and exposure, does anyone have other strategies? We emphasize the use of a 2-column t-chart table structure to arrive at the conclusion that LHS = RHS. Thank you!

• Math
• 11
• Differentiation / Planning

3

• Jul 7, 2014 11:37am

Michael,
I've always done it the same way as you and I agree that it just goes over some students' heads. Hopefully if they are in a class doing trig then their algebra skills should be strong, but of course this is not always the case. Having them practice after you show them some examples is the only thing that has had some success for me. Interested to see if anyone else has a good idea. Thanks for putting the question out there!

Lauren

• Jul 7, 2014 1:43pm

Lauren, I appreciate your response. There's a few strategies I have not tried and I think I'll resort to those too later in the course. When I taught it, I felt that alot of students did not practise on their own during the spring break. I really had to spoon feed them, I feel. Thanks again.

• Jul 15, 2014 5:22am

I like that scaffolding idea, Douglas! Thank you.