[问答题]
Show that for an isotropymjbjx4o+4 2av s;d *ni;bjhsy5*c y 3ip6qes4c solid, $\beta$ = 3$\alpha$ if the amount of expansion is small. $\beta$ and $\alpha$ are the coefficients of volume and linear expansion, respectively. [Hint: Consider a cubical solid, and neglect very small quantities. See also Problem 18 and Fig. 13–30.]
