Let S be an oriented smooth surface containing a circle of radius 1 and a straight line, which intersect perpendicularly at a point $p\in S$. Show that if the Gauss curvature K of S satisfies K(p)=0, then the mean curvature H of S satisfies $∣H(p)∣\leq 1/2$.
I tried to solve the exercise above, by the principal curvatures k_1,k_2, $K(p)=k_1\cdot k_2 $ and $H(p)=\frac{k_1+ k_2}{2}$ by hypothesis lets say $k_2=0 $, I also know that the curvature of a straight line equals 0 and the curvature of unit circle is 1, I was thinking Meusnier’s Theorem but I can't make any progress .