A plane is drawn through the
midpoint of a diagonal of a cube
perpendicular to the diagonal.
Determine the area of the figure
resulting from the section of the
cube cut by this plane if the edge
of the cube is equal to a.
Is definite integral can have negative value?
Because I think ∫_a ^b f(x) dx is total area below
graph f(x) from x = a until x = b, so it can′t
be negative