Ok this is not a problem, to calculate points on 2D you can always use the "translation of axes", problems arise when you do it in 3D.
However in FreeCAD sources I'm almost sure that there is less involute way to do it, but as usual, it's a well hidden secret in "clear view".
To be more precise, if you know vector math there will be no problem to rotate things, if you don't have a good mathematical education, you will revert to use "simple math", I have used this way many times, for example to calculate vertexes of regular polygon or to obtain angle between two lines (in 2D space), as FreeCAD has some methods, but are taylored to to things differently and sometimes give some "counter intuitive" results (from my mathematically impaired mind )
a side note, I hope that your angle is in radians as python math.sin and math.cos expect angles in radians:
# Return the sine value of 30 degrees
# Return the sine value of 90 degrees
My former post was an answer to the way to obtain the 3D coordinates having the mouse positions, as used in some FreeCAD sources I've found.
If you are speaking of Sketches, there is no problem, I hope if you are using the normal convention that sketches are in the XY plane, but I fear that is possible to have sketches in other planes (maybe a remember wrong) so it has to be checked if your math is working also for a sketch as example in XZ or YZ plane.
If the formulas are for your "personal use only" no problem, as you know that your math works in XY plane and when obtained the wires, you could rotate them as you need, but for example if they are to be put in a Macro, it is another story.