想了很久了,he is to do his work well.怎么来的.

想了很久了,he is to do his work well.怎么来的.A workman must sharpen his tools if he is to do his work well.是"工欲善其事,必先利其器"的意思!1 我想知道he is to do his work的句型分析,is 和to怎么挨一块了啊?挺奇怪滴!2 为什么不用he do his work well.