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 194
zparallel to OZ. Thus x and y are the horizontal co-ordinates, and z is the vertical co-ordinate. A co-ordinate has a negative value when the point issituated on the other side of the plane from which thatco-ordinate is measured. Thus z would be negative for anypoint below the horizontal plane XY.… … The student will note that the co-ordinate planes, whenextended eacli way from 0, divide the neighbouring spaceinto eight trihedral angles. He should also note that whenthe co-ordinates of a point are given in sign and magnitude,the signs tell us in which trihedral angle the point issituated, and…
