The mathematics episodes are a curious mix of comfortable and frustrating to me. It’s comfortable particularly in hearing about stuff I’m already at least somewhat familiar with. But then it frustrates me when I hear familiar old anecdotes and metaphors and explanations hauled out. It feels like a waste to repeat thoughts others have had for us.

]]>I think you will be fine if you pick the same day for each month. The US Navy link I included in the post has all of that data. You just enter your location, and pick which day of the month you want to use.

We used our TI-84 calculators to derive the regression equation (STAT/CALC/SinReg). From the equation the TI-84 gives you, you can get a, b, c, and d. You can also calculate them by hand, if you want. For example, the period is 12 months, so b = 2pi/12. Desmos has a built-in regression feature now, if you want to use that. We set up a general y = a*sin(b*(x-c))+ d function with sliders for a, b, c, and d, and used trial and error to match the data. I hope this helps; good luck with your presentation! ]]>