yeah, s has them done for you already as expressions
under the expression list
"get rotated x/y from offsets does this"
S.xoffrot(origin x, origin angle, x offset, y offset)
S.yoffrot(origin y, origin angle, x offset, y offset)
origin x or y would be your hotspot, or sprite location
angle is the sprites angle
x and y offset are your imagepoint x and y
and it returns the x location of where the imagepoint would be
The "get x offset" and "get y offset" expressions do the reverse
if you have a thing that you want to be the new imagepoint, but your sprite is already rotated, so you need to retrieve these rotated x and y offsets, you do that with those expressions
maybe I'll add those to the math plugin next, since it'd be a simple copy/paste job