Sinusoidal assignment demo
This video tells you how to 1) understand how to transform a graph; and 2) how to actually make the graph fit data as close as possible in desmos.
I spotted a few errors (times are approximate):
1) 13:52 327 is amplitude not wavelength
2) 15:11 wavelength is not 8, it is 12, for months in a year
3) 19:22 This is not exactly an error, but the reason for 30(x-1) being passed into cosine instead of 30x was edited out due to poor video quality. The simple fact was that 30x failed to map on to the same points as the sine function, so I shifted the graph over by 1, and succeeded. I am thinking that the reason it works is because "30x" assumes the population cycle starts from month 0, when it really starts from month 1.
It is possible that there are other errors in this video, but most of them are relatively minor.