The state of stress at a point on the upper surface of the airplane wing is shown on the element. Determine a) the principal stresses and b) the maximum in-plane shear stress and average normal stress...

The state of stress at a point on the upper surface of the airplane wing is shown on the element. Determine a) the principal stresses and b) the maximum in-plane shear stress and average normal stress at the point. Show the orientation of the element reference frame in each case.