 Greetings. In your trigonometry course, you may have learned how to fit a sinusoidal model to specific data. The sinusoidal model is generally a sinusoidal equation. You may have even learned how to use your Texas Instruments graphing calculator to find the so-called sine regression equation that best fits the data. In this screencast, we're going to show how to do that using GeoGipro. We're going to show how to plot the points and to find the so-called sine regression equation. This sine regression equation is one that has a mathematical criteria that it satisfies to be categorized as the best fit equation for the data. We are not going to discuss what that criteria is, but just be aware that there is a criteria that is satisfied mathematically that allows us to call this the best fit, at least according to that criteria. Here's the data we're going to use. This shows the number of daylight hours for Edinburgh, Scotland. What we are going to do is use GeoGipro to plot these points and to determine the sine regression equation. We're going to let y be the number of hours of daylight and t be the time measured in months, with one for January, two for February, and so on. This is important to specify how you're defining your variables. Let's take a look at GeoGipro. One thing we want to do here is plot points. A very good option to do this is to use the spreadsheet view. Right now we have the algebra view and the graphics view visible. All we have to do is say, okay, let's take a look at the spreadsheet view. Now to save a little time, I have already entered half the data into the spreadsheet view. We might even want to shrink this a little bit. We are only going to use those two columns. Now what we do is fill in the rest of the data. In the first six rows, we're done in exactly the same manner. I'm going to try to save a little time and just go 7, 8, 9, 10, 11, 12, but you should just feel free to enter the data as you best see fit. So 17.48 is the data for July, 16.03 for August, 13.82 for September, 11.52 for October, 9.18, and 7.40. And there we have the data entered. Now what we want to do is plot those points. And actually that's pretty easy in GeoGipro. With the spreadsheet, just select those 12 rows. Those are the 12 points we're going to plot. Come up here to this menu, which basically is create list, and what we're going to do is create a list of points. This will say, okay, what do you want to name that? And I'm just going to leave it at list one, but you can change that name if you desire. So say create. Okay, nothing really shows up because the data screen is not appropriate. So again, it might be nice to now dispense with the spreadsheet view and just have this. And now I start adjusting the viewing window. And in particular, it looks like we want to change that y-axis. Now you can see some of the points coming in. We might move this over and like to keep the origin in there. So we might need to adjust the x-axis slightly, and that should do a pretty good job. We can drop that a little bit. And there we go. So there's our data points. Now what we can do is basically enter what is called the fitSign command. Basically, I'm going to use function notation f of x equals, and that's basically fitSign. And if you notice the pop-up here, it says what you need are brackets and a list of points. So we put in the brackets, and the list we're going to use is right up here in the Algebra view, list one. So I just type in list one, hit enter, and there we have the sign fit. And again, we can even dispense with the Algebra view if we want, and we get something like that. Then again, it might be nice to readjust the viewing window, but we have a very nice image of that. Now here's another nice thing you can do, which we haven't done before. This is the first time it's introduced. You can enter text into your graphics window, and that's this insert text up here. Actually, it might be nice to have the Algebra view here for the time being. And what I'm going to do is just hit insert text and come down and put it someplace in the graphics screen. And something will come up. Without going into a lot of details of this, there is what are called dynamic text, static text and dynamic text. We're going to use a dynamic text, and what you do is put a double quote, notice it says invalid input. That's okay, don't worry about that yet. Y equals, finish the quote. Now it says the preview is okay, and now all I'm going to do is type in the name of the function I want to follow that. It's just going to be F, and hit okay. And now that sign regression equation is part of the graphics view. If you want to change your rounding options, we can change that say to three decimal places. And we get something like that. You can even, if you right click on the text there, you can go down to object properties. And the text, this gives you the size. Actually, you can change the font, but instead of small, let's put in large. And what we will see, I hit okay on that, close that up, and now I've got a larger view of that. I can move that around and put that where I want that. So there is a very nice way to get the sign regression. I just closed the algebra view, and now we have a nice image of the points, the equation, and the graph of that equation. Nice way to do that, we can of course now copy this and paste it into a word processor. That's it for now, so long.