Since this little program has generated so much discussion today (mostly via email), I thought I’d share how I used Jing tonight in a Virtual Office Hour…

This is right from my live chat tonight in my calculus class (my response to this problem is to **follow up** the 12 or so student posts)… the “cut and paste” part is because URLs are not “live” in the chat room. Plus I don’t want them to get accidentally booted out of “chat.”

*me: The problem is to find the values of a and b in order to make the piecewise function continuous. Here’s the function (cut and paste URL into separate browser window) **http://screencast.com/t/bbjcb3nrf** **me: The only piece that you know for sure is the first one. Where is the problem value for the first piece? **student: at x=2 The first part is equal to x+2**me: so when x=2, what is y?**student: 4**me: So now, in the second function we know it has to go through the point (2,4) or it won’t be continuous. **me: So, using y=ax^2-bx+5, substitute x=2 and y=4. You should end up with an equation that still has a and b. **student: 4a-2b=-1.**me: Okay… now… the last two equations must also intersect at x=3. So we set these equal to each other and use x=3 because that’s where the last two pieces switch. **http://screencast.com/t/ezrIzNJeDJ** **student: why is it that we use x=3?**me: because that is where the function jumps from one piece to another and the functions must be equal at their endpoints to be continuous.**student: okay**me: Now we solve the system of equations…**http://screencast.com/t/zxloCbrM** *

And that… is how you use Jing in a math chat! Each video took about 1 minute to upload… (but I’m on satellite high-speed internet, so probably it would be faster for most people with regular high-speed internet)

Please post your comments in the “comments” area (instead of in email) so that all readers can get the benefit.

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