Graph paper, parallel, and planimeter methods are current tools for acreage calculation.

目前常用的量算积法有格纸法、线法、求积仪法。

Parallel lines are lines that never join.

线是永不相交的线。

Parallel lines are, by definition, lines on the same plane that never join.

按照定义说, 线是在同一上永不相交的线。

Zollner's illusion makes parallel lines seem to diverge by placing them on a zigzag-striped background.

将线置于锯齿形条纹背景上，左氏错觉会让线看起来不。

There are two parallel lines.

有两条线。