Write equations for the horizontal and vertical lines passing through the point $(2,1)$. horizontal line: vertical line:

Step 1 ：The problem is asking for the equations of the horizontal and vertical lines passing through the point (2,1).

Step 2 ：The equation of a horizontal line passing through a point (x_0, y_0) is given by y = y_0. So, the equation of the horizontal line passing through the point (2,1) is y = 1.

Step 3 ：The equation of a vertical line passing through a point (x_0, y_0) is given by x = x_0. So, the equation of the vertical line passing through the point (2,1) is x = 2.

Step 4 ：\(\boxed{\text{The equation of the horizontal line is } y = 1 \text{ and the equation of the vertical line is } x = 2}\)