Maths, physics, chemistry, technology...
I sometimes forget whether you flip the rotate the matrix by 180° or mirror it on an axis when I didn't do any linear algebra for a while. However, that doesn't happen too often lately. I guess it's easier to remember if you see it visualised like that.
I agree with you. I thought the sin(x)/cos(x) .gifs were pretty bad but still acceptable on some, but that one was just irredeemable. Everyone should be able to visualize something as simple as taking the transpose of a matrix.
why is supergiant a larger class of star than hypergiant? Get your shit together astronomy.
It's based on mass and luminosity. Red supergiants can be smaller than blue hypergiants. There's a big explanation but tl;dr it's based off a function of energy emitted per unit time per area, mass of the star, and planck's law.
Generally, the hotter you get, the more luminous you are, the bluer you get, and your radius doesn't increase as much as your mass. However, cooler stars are redder, they have less luminosity, and their radius increases far more than their mass.
Hertzsprung-Russell diagrams really explain this.