This is a special case problem of a Cube and the sectional plane angle will not be given. Instead its given as the true shape of the section is a Regular Hexagon.
Question:
A cube of 30mm edges is cut by a sectional plane so that the true shape of the section is a regular hexagon. Draw the projections of the cube and find the inclination of the section plane with HP. Also measure the length of the sides of regular hexagon in the true shape of the section.