This is the second cardinal point which the cultivator should keep in mind.

这是第二个基点的耕耘应该牢记。

One cardinal point the planners hammer ed out fast. Building new ships to replace U-boat sinkings came first.

计划人员很快就确定了重点，那就是首先要制造新船以补充被德国潜艇击沉的船只。

With used Newtons image formula of spherical refraction and the optical spacing term, the formula about cardinal point and image of the thick lens is derived with simpler and more natural way.

利用折射球面成象的牛顿公式及光学间隔概念，更加简洁地得出了有关厚透镜成象的基点及物象公式。