Is there an algebraic formula for determining an angle of reflection using only the angle of the ray and the angle of the wall?

Answer 1

Let r be the angle of the ray, and R the angle of reflection.

If the wall is flat (i.e., if its angle is 0), then we know that r + R = Pi/2.

Now suppose the wall has angle w. Then rotate the diagram by -w,

so that the wall is now flat again, and the angles of the ray and its

reflection are now r - w and R - w, respectively.

We then have (r - w) + (R - w) = Pi/2, which should give you enough

information to find R.