How to get eponential regression to give solution in y=a.e^kx format

[Colin STEVENSON]

Students at my school are using probes to capture cooling results for Newton Cooling Experiment.

 

When they analyse using expontenial regression they receive y=a.b^x whereas the teacher wants the form y=a.e^kx so that they can interpret the k value.

 

I am hoping some body can help me out.

 

Thanking you in advance,

Col Stevenson

[Nelson Sousa]

I think the Nspire only presents an exponential regression as a*b^x,
there's no way to present it differently.
You have to compute ln(x) to change the notation, as a*b^x = a* e^(ln(b)*x).


Cheers,
Nelson

[Sean Bird]

If instead of using a regression, students could plot an exponential function and use the grab and translate capabilities to come up with a nice approximation for best fit.
For example, graph f1(x)=2e^(-3x)+23
I chose 23 as the vertical shift because that is a reasonable room temperature on the Celsius scale. The other numbers I just made up to put a graph on the screen that will be manipulated when the student presses CTRL CLICK on the graph.

Another option would be to graph
f1(x)=a*e^(k*x)+c
and use MENU > Actions > Insert slider
to make sliders for 'a', 'k', and 'c'
To see a bit of what I mean look at page 2.2 of the tns file or video from this timath calculus activity http://www.timath.com/calculus/732

If anyone is in Southern Florida, it would be great to see you at the NSTA meeting in Ft. Lauderdale this week. On Thursday I'll be presenting on data collection and assessment with the TI-Nspire CAS & TI-Nspire Navigator.

Have a great week,
 Sean Bird

[Colin STEVENSON]

Nelson

Thanks for the quick reply and work around

Col