In this paper, we study the regularity and analyticity of solutions to linear elliptic
equations with measurable or continuous coefficients. We prove that if the coefficients
and inhomogeneous term are Hölder-continuous in a direction, then the
second-order derivative in this direction of the solution is Hölder-continuous, with a
different Hölder exponent. We also prove that if the coefficients and the
inhomogeneous term are analytic in a direction, then the solution is analytic in that
direction.