To determine the coordinates of vertex A′, we need to know the coordinates of vertex A and the line of reflection.
Let's assume the line of reflection is a vertical line, say \( x = k \). The reflection of a point \( (x, y) \) over a vertical line \( x = k \) is given by the formula:
\[ (x', y') = (2k - x, y) \]
This means the x-coordinate of the reflected point A′ is determined by twice the line of reflection's x-coordinate minus the original x-coordinate of point A.
If you can provide the coordinates of vertex A and the line of reflection, I can calculate the coordinates of vertex A′.