One line cuts another at right angles.
一条线与另一条线成直角相交。
An early instrument for measuring altitude of celestial bodies, consisting of a90= graduated arc with a movable radius for measuring angles.
象限仪用来测量天体纬度的一种早期工具，由一个有90度刻度的圆弧和一个用来测量角度的可移动的半径构成
At right angles to a vertical line.
横的与垂直线成90度角的
