Tuesday, February 11, 2014

Analyzing Exponential and Logarithmic Graphs

As I was looking ahead in my unit of exponentials and logs in Algebra II, I opened up a lesson plan whose first page read, "Note to self: This lesson sucked. Kids were totally bored."

Must have written that a year ago and forgotten...until now.

This is a topic that I teach in PreCalc also, so I was motivated to change this boring lesson.  But worse than being boring, my lesson honestly did not have kids exploring interesting mathematics.

What I really wanted was for kids to understand the inverse relationship between exponential and logarithmic functions before we talked about solving equations.  I wanted them to start to understand what happens graphically before we explored the analytic implications.

So, I made this matching activity.  I really broke it down for my Algebra II kids, but I think PreCalc students (or advanced Algebra II students) could dive right into it with little to no instruction on the teacher's part.  I limited the transformations of the graphs to shifts only, but, for more advanced students, it could be nice to show reflections also (though I might stay away from stretches/shrinks...).

I had my Algebra II students work ONLY with the exponential graphs first.  They shared a deck of cards with a partner, but each student was to fill in his/her own chart. Once they were done with that side, I had them figure out which log graph was the correct inverse for each exponential graph.  Lastly, I had them analyze the log graphs.

The activity is designed so that students can see the similarities/differences of exponential and log functions, beyond just "x's and y's switch."  Ok, so they switch...what does that mean?  If I have an exponential graph that shifted to the right 2 units, which direction will its inverse graph shift?  Why?

I think this was a considerably more interesting way to get kids more comfortable with log graphs.  And they were definitely noticing the types of patterns I was hoping they'd notice.  The nice thing is that since a lot of the patterns are obvious, kids can quickly check their own work for errors once you've had a discussion as a class about all the similarities that should occur in their charts.

Chart to record results (and key):



Deck of cards (6 exponential functions and their corresponding logarithmic inverses)--thanks as always, Desmos!:



A couple of the matches

4 comments:

  1. Rebecka,

    You are awesome. I used this activity today in class! It was fun and beneficial, I thought! :)

    Love your posts.

    ReplyDelete
  2. Do you know that Hotmail account is also Outlook.com account? More info is on hotmail email login

    ReplyDelete
  3. Students can download TS Inter 1st & 2nd Year Model Paper in PDF format from this web page below given links. Telangana Inter 1st & 2nd Year Exam are organised by Board of Intermediate Education Telangana Only. Regular and Private Students in BIE Telangana Students must register for the public exam after preparing for their exam using these sample papers TS Inter 1st & 2nd year Model Paper Inter 1st & 2nd Year Time Tables are also available on this website for students. Students benefit from the BIE Telangana Inter 1st & 2nd Year Bit Bank and Question Bank because they provide a solid practise example for solving papers effectively.

    ReplyDelete

Tell me what you think!