$\backslash (7\mathrm{.}8^\{*\}\backslash )$ For the given state of stress, determine $($a$)$ the princt$-$

Stress on the plane showin $($at $30.)$

$\backslash (7\mathrm{.}12^\{*\}\backslash )$ For the given state of stress, determine $($a$)$ the orientation of the planes of maximum in$-$plane shearing stress, $($b$)$ the corresponding memal stress es

$*$ use equatious

$7\mathrm{.}32$ Solve Probs. $7\mathrm{.}8$ and $7\mathrm{.}12,$ using Mohr's circle.