$8\mathrm{.}18-8\mathrm{.}20.$ Use the unit$-$dummy$-$load method to compute the horizontal

and vertical displacements of points $A$ of the structures shown. All

members are linearly elastic and the truss members have equal cross$-$

sectional areas. Neglect shear deformations.

Fig. P$-8.18$

Fig. P$-8\mathrm{.}19$