Understanding the Solution Manual for Mechanics of Materials (3rd Edition) by Roy R. Craig
The shear modulus can be calculated as:
Result for (a): The principal stresses are 15.31 ksi (tension) and 7.31 ksi (compression). The maximum principal stress acts on a plane oriented $22.5^\circ$ counterclockwise from the original $x$-axis. Understanding the Solution Manual for Mechanics of Materials
Solution