In a dihedral angle of measure c two non-intersecting spheres are inscribed, the centers of which are located on a straight line perpendicular to the edge of the dihedral angle. The points of contact of these spheres with the edges of the corner are at distances a and b from the edge. Let us consider an arbitrary plane tangent to these spheres and intersecting the segment connecting their centers. Let us denote by ϕ the measure of the angle formed at the intersection of this plane with the faces of a given dihedral angle. Find the greatest value ϕ. geometry3D geometrysphere