Final answer:
The question involves calculating stress transformation for a 30° counterclockwise rotation using equations and then comparing the result using Mohr's circle.
Step-by-step explanation:
The question deals with stress transformation at a point in a material, specifically how the state of stress changes when the material is oriented at a different angle from its original orientation. To find the new stresses after a 30° counterclockwise rotation, we use stress transformation equations for plane stress. The original stresses given are σxx = −8 MPa, τxy = −6 MPa, τxz = 0 MPa, σyy = 12 MPa, τyz = 0 MPa, and σzz = 0 MPa. For part (b), we will compare the transformed stresses to the ones obtained via Mohr's circle, which is a graphical method for finding principal stresses and stress transformation.