Final answer:
The equation of the plane containing the line in the xy plane where y=1 is simply y = 1, representing a plane parallel to the x-axis and including all points with y as 1.
Step-by-step explanation:
To find an equation for the plane containing the line in the xy plane where y=1, we look for a plane that is parallel to the x-axis and includes all points where y is always equal to 1. In the three-dimensional space, a plane equation is generally given by Ax + By + Cz + D = 0. Since the plane is parallel to the x-axis and does not vary with z (height), the coefficients for x and z should be zero. Thus, we get the equation for the desired plane by simply stating that y is always equal to 1, which means the equation is y = 1.