Exercise 4, § 3

Let E be a locally convex Hausdorff space, E' its dual. If M is a closed vector subspace of E which is metrizable and distinguished (IV, p. 52, exerc. 4), then the strong topology $\beta(E'/M^\circ, M)$ is the quotient topology by $M^\circ$ of the strong topology $\beta(E', E)$ (use exerc. 3, b) and IV, p. 51, exerc. 22, b)).