i have been trying to understand the graphs and what they mean

i see that some area on the wave have 90 degrees angle despite it not being the little box that indicates right triangles and then suddenly it turns to 270 while in similar graphs that same place would be 180 despite the wave size being the same

anyone have the ability to simplify this?

tangent seems even more complicated what does the twisted line have to do with it being a division of sine and cosine