Input (x) 0,1,2 output (y) 3,5,7 what is the rule?

You have not attached a picture of the triangle.

180 degrees complete a triangle so maybe if an angle is given + 90 degrees if its right angle then 90- other angle = angle p.

You would need to see if any other angles given and if not then you would need to see if any straight parallel lines or adjacent or even consecutive angles given if not then angle p could be worked out from a side given.

If its an opposite side and adjacent then we use shift Tan-1  side/side

If its an adjacent side and hypotenuse we use shift Cos-1 side/side

IF its an opposite and hypotenuse given we use shift Sin -1 side/side