How is Mohr's Circle used in stress analysis?

Mohr's Circle is a graphical method to determine stresses on any inclined plane from known stresses on orthogonal planes. The circle's center is at (σx + σy)/2 on the σ-axis, with radius √[(σx - σy)/2]² + τxy². Principal stresses are at the circle's intersection with the σ-axis, and maximum shear stress equals the radius. It's widely used in FEA post-processing.