I use a lot of formulas where say, if sprite is moving 0 speed, I want angle set to 20 and if the sprite is moving 200, i want the angle set to 360 and everything in between

which is pretty simple. I just punch the numbers into a two point form calculator and it gives me the y= and I plug it in (angle = 1.7*speed + 20 in this example)

which is easy enough. but let's say I want to add a curve to that line (so the angle changes slower at slower speeds and faster at faster speeds), what's the math I'm looking for? I used to know these things.. just need a reminder.

Thanks!