Practical plane and solid geometry for advanced students, including graphic statics, adapted to the requirements of the South Kensington syllabus (1899)
Harrison, Joseph, Baxandall, George Albert · London Macmillan · leaf 494
lect any point p in Im. Draw the two tangents qp,np. Draw the triangle with base angle a, and along its baseset off HyNv HXQX equal to pu,pq. Erect the perpendicu-lars dVlPv QXPV and mark off their lengths as heights abovexy on the projector from p, thus obtaining/, p. Determine other points… … Thus the envelope is the helix itself. The surface hasan edge, which coincides withthe helix. The figure shows how a model ofthis surface may be made. Set out the symmetrical curveson cardboard, and make holes atthe points determined by a series ofequiangular tangents. Indent andfold along the…
