## Thomas' Calculus 13th Edition

An Elliptical cylinder along y-axis as shown in $\bf{Graph(b)}$
Given: $x^2+2z^2=8$ ....(1) Re-write as: $\dfrac{x^2}{(2 \sqrt 2)^2}+\dfrac{z^2}{(2)^2}=1$ ...(2) Hence, the equation (2) shows a graph for an Elliptical cylinder along y-axis as shown in $\bf{Graph(b)}$