Model for Descriptive Geometry by A. Jullien - Through a Given Point Construct a Plane Perpendicular to a Given Line

Jullien, A. · ca 1880

The black string represents the given line bc’, while the point (a, a’) at the bend of the wire represents the given point. The horizontal line coming out of the vertical plane denoted cd’ is perpendicular to line bc’. Point P is the intersection of the vertical and horizontal projections of the wire with the x-axis. It follows that plane FPF’ which contains the line (c,0)-(0,d’) (wire) is also perpendicular to line bc’.