Note on a Formula in Solid Geometry

The axes being oblique to find the angle between two directions whose ratios (x₁, y₁, z₁, (x₂, y₂, z₂) are given by the equations

T = ux + vy + wz = 0, ...                                       (1)

S = ax² + by² + cz² + 2fyz + 2 gzx + 2 hxy = 0. ...     (2)

With reference to the solution of this problem communicated to the Journal (June 1923) by Prof. E. H. Neville.