Digging deeper into Scratch: trigonometry and maths formulas

Hi everybody! I'm not sure if this is the right place to ask... Recently I've become interested in a series of projects with mathematical and trigonometric formulas inside, usually related to effects with PEN. I understand most of the code when I go through it but I get lost (cause I'm obviously rusty;-) when I come across these sin, cos, etc. So I'm wondering if there are any kind of materials, websites, forums... that can help me revise, understand and apply these. Thank you so much!