Problem $1$:

The truss shown in Figure $1$ is made of steel for which the modulus of elasticity, $E=200$GPa. All members have the

same cross$-$sectional area, $A=4250m{m}^2.$ Use Castigliano's Theorem to determine:

a$)$ the vertical displacement at joint $A$ or $C.$

b$)$ the vertical displacement at joint $B.$

Figure $1$