in the name of god, the most beneficent, the most merciful

math: trigonometry

here’s some visuals of basic circular functions

trigonometry-functions

thanks to https://simpliengineering.com/t/origin-of-trig-terms-tangent-and-secant/1886

there’s also a good comment following by the user BAretired:

I love that diagram of a circle of unit radius. It makes everything so clear and actually gives us a rough idea of approximately what size the various trig functions should be.