1.The vertical line of a projection plane 投影面垂直线 (H-plane, (H-perpendicular (铅垂线) Definition If it is vertical to the V-plane,it is called aV-perpendicular line. (正垂线) 定义 W-plane, W-perpendicular (侧垂线) 与某投影面垂直的直线称为该面的垂直线。 Obliquity horizontal 倾角 Bis the oblique angles of the corresponding line formed with the frontal plane. profile 与H面的夹角：@；与V面的夹角：B;与W面的夹角：y。(均为0°或90°) Characterist its projection on its vertical plane converges to a point. 投影特性 投影面垂直线在所垂直的投影面上的投影积聚为一点。 Its projections on the other two planes are both parallel with an axis of projection,and shows its true length. 在另外两个投影面上的投影均平行相应的投影轴，且反映实长。 H-perpendicular line铅垂线 V-perpendicular line正垂线 W-perpendicular line侧垂线 c7d)Z f Z e"f" AB “AB CD EF 0 CD EFW-perpendicular line侧垂线 Z ● e f e f e(f) X o YH YW α horizontal βis the oblique angles of the corresponding line formed with the frontal plane. γ profile 与H面的夹角:α；与V 面的夹角:β；与W面的夹角:γ。（均为0或90） H-plane, H-perpendicular (铅垂线) If it is vertical to the V-plane, it is called a V-perpendicular line. (正垂线) W-plane, W-perpendicular (侧垂线) 与某投影面垂直的直线称为该面的垂直线． Its projection on its vertical plane converges to a point. 投影面垂直线在所垂直的投影面上的投影积聚为一点。 Its projections on the other two planes are both parallel with an axis of projection, and shows its true length. 在另外两个投影面上的投影均平行相应的投影轴，且反映实长。 Definition 定 义 Obliquity 倾 角 Characteristics 投影特性 1. The vertical line of a projection plane 投影面垂直线 请 点 击 鼠 标 左 键 显 示 后 面 内 容 H-perpendicular line 铅垂线 YW ● a b a(b) a b X Z o YH AB AB V-perpendicular line正垂线 ● c(d) c d d c X Z o YH YW CD CD EF EF