 So here we have the scenario of an array of photovoltaics that are set up one row behind the next. They're each going to have a certain tilt. That tilt is represented by beta, and each one is going to have a common collector azimuth of gamma represented down here. That gamma, again, is that planar rotation. In this case, the array that you're seeing is rotated 9 degrees towards the east. So minus 9 degrees of rotation, or 9 minus 180 degrees to give us our azimuth. The distance between the panels right now is just specified as D. And the panels themselves are going to have a shadow. And that shadow is going to change over the course of the year, as the sun is high in the sky and low in the sky. And what we really like is for these panels to be spaced appropriately such that they do not block each other. Because this is one of our mechanisms for the goal of solar design. We want to maximize the solar utility for the client or stakeholders in a given locale. And in this locale, we want to know how far apart we can space these to collect the energy to basically avoid or remove shading from the spacing of these panels. So what you're seeing is a system that we're going to define in terms of critical points. We're going to take those critical points and we're going to plot them on a diagram. So the first thing is how do we list these critical points? Well, now we don't have a central point X. Now we actually have three points for each one of the panels across the top and across the bottom. This guy's going to be behind here, you won't see it. But you're going to have three points along the bottom, three points along the top. The points along the top are ultimately going to shade these critical points along the bottom. So I'm going to name these critical points A, B, and C. And the points that we will be referring to in terms of what kind of shading are we expecting, we're going to label one, two, and three. Right? So now going into this, you're looking at this from the side and you're seeing a system like this, right? There's going to be a certain tilt, beta. The beta is going to be the same for both collectors and they are going to be separated at a certain distance, D. That's either going to be the spacing from top to top or from bottom to bottom. It's the same spacing with D, right? So looking at this, we want to basically compare any point one and what we really like to see is how does one compare to point C? Excuse me, point C is down here. So let's go one to point C, one to point B, and one to point A. That's one of our first questions. And then after we've done that, we're going to look at how does point two compare to point C, critical point C, critical point B, and A. And then we'll finally finish that with three C, three B, and three A. And what we should be able to see is that because of similar geometries, we're going to find some kind of similar responses in terms of all of these geometric relationships. And I can show you that. Again, this is in the textbook, but if I bring this up right here, you're going to see that I've got a table of points, one A to A, three A, just like we were talking about. And one B to B, three B, one C, two C, three C. They each have their own set of altitude angles, right? And you're going to notice that there are certain one to one degree common altitude angles just due to common geometries. Similarly, you're going to see common 41 degree angles and two 12 degree angles, right? Looking at the azimuth angles, the zero degree azimuth corresponds to 180 degree in the meteorological standard and so on down. We're seeing that 76 degrees is equivalent to 250 degrees and minus 64 degrees is equivalent to 116 degrees. So we're going to take these points as 180, 244, 256 for the azimuth angles of the collector. And we're going to plot those in the next plot and we'll plot the alpha angles. And what we're going to come up with is basically something that looks like the cross-section of a loaf of bread, right? It's going to have two vertical sides and it's going to have an arc in the middle.