I needed to learn some trigonometry for something I wanted to make a few months ago. I didn't get round to it. I tried to make something today and it didn't take long to realise that I needed some trigonometry to properly write a cubic bezier (a sentence that I am barely smart enough to write let alone understand and execute).
While I'm sure I learned trigonometry in school, I do not remember any of it. If my life depended on it I don't think I could explain what cos, tan, and sin mean to a level that would satisfy this imagined murderous mathematics nerd.