I am a bit confused about the part about the angle of the slope affecting the amount of incoming solar radiation received. Wouldn’t this example with the equator receiving sunlight in a perpendicular direction only be true during spring and autumn? So calculating the “optimum” angle as equal to the latitude would only work during these precise times, and at other times in the year you would have to subtract whatever angle the latitude is where the sun’s rays are perpendicular, which was explained (very nicely!) in video 3.1. Is this right or is there something I am missing?
Perhaps it is averaged over the year, so the slope that gets the most sun over the course of a whole year is equal to the latitude?