Thursday, February 05, 2009

Polar Graphs

I'm so excited. I taught the graphing r= 4 sin(theta), r = 2 cos(theta) + 3 and such today, and I think THIS method will stick more successfully than what I've done in the past.

Two years ago at the NCTM Atlanta Conference, a teacher from North Dakota shared her strategy, and it made so much sense, and this year I adapted it and tried it.

I made up a packet where I have 12 such graphs mapped out on a rectangular coordinate system. I don't even label which ones they are. Right next to these graphs are blank polar coordinate systems. The tick marks (or angle marks) on each are divided the same (into pi/6). This ND teacher stressed to make the connection between "y = f(x)" and "r = f(theta)" and link x to theta and y to r and to keep mentioning it. Then you transfer each point from (x,y) to (r,theta) accordingly, and voila! You have your graph.

On the front page I had 3 similar ones, and after they/we graphed all three, then we refreshed our memory on what the equations were. Then we discussed what the connection was between "amplitude BIGGER/smaller than vertical shift" was, etc.

We got through 4 in class, and they have the rest for homework. I'm thinking it will work, because even I can now remember what the graphs should look like by doing such an analysis (whereas before, I had to refresh my memory each year).


  1. That's cool! Mad me print out some polar graph paper and play!

  2. Anonymous1:47 PM

    I like it - thanks!

  3. I’m going into the teaching field (Middle School Math) after 25 years in the I.T. field. I have had a number of classes on teaching theory and I am always interested in what veteran teachers have to comment on in relationship to what I’m being taught in my education classes. The steps 2 and 4 that you mentioned are a good summary of getting students engaged in the learning process… a very good video on motivation is

  4. I sure could have used your help last week when my daughter was struggling with her Algebra class. Her teacher "only teaches for 5 minutes and then expects us to get it on our own."

    Don't worry. I know that's 17 yo talk for "I don't get it."

    My principal (who has a degree in math) spent an hour with me to show me how to tutor her) and it was kinda fun! It's been over thirty years since I've done high school algebra!